Rabbi Mordecai Kaplan, Reconstructionist Mahzor p.190
From the cowardice that shrinks from new truth
From the laziness that is content with half-truths,
From the arrogance that thinks it knows all truth,
O God of Truth deliver us.

https://americanmussar.com/american-mussar-cycle-6-truth/
The goal of the practicing the Truth Soul Trait is to learn to appreciate the Truth from another’s perspective, and to exercise judgement about how much of your Truth to share with others.
Too Little Truth: People will lose trust in us, and will not believe us even when we are telling the truth.
Too Much Truth: Unkind and hurtful speech.

Spectrum of Truth

Yevamot 65b:7-9
And R. Ilea said in the name of R. Eleazar b. R. Simon: A person may edit what has been said for the sake of peace, as Joseph’s brothers said “Your father commanded… please forgive.” (Gen 50:16)....The school of R. Yishmael taught: peace is so important that even God altered what was said for its sake! For at first, [Sarah says] “My husband is old” and afterwards, [when God repeats her words to Abraham] it says “I am old.” (Gen 18:12)

Rabbi Lisa L. Goldstein, "Emet- Truth, Hidden and Revealed," Block, Rabbi Barry, The Mussar Torah Commentary: A Spiritual Path to Living a Meaningful and Ethical Life (p. 38-9).
What is going on here? How are we to understand the actions of our mythic ancestors and their apparent complete disregard for the “truth” (emet, אֱמֶת)?
The truth about truth is that it is not always so simple. We get a glimpse of this uncomfortable reality in a midrash about the creation of the first human being. Rabbi Shimon taught that when the Blessed Holy One decided to create the first human, the ministering angels divided into opposing blocs, some of whom said that humans should not be created, while others said that humans should indeed be created. The Angel of Loving-Kindness and the Angel of Justice argued in favor of the creation of humans, who would strive to do acts of loving-kindness and justice. But the Angel of Truth and the Angel of Peace disagreed. The Angel of Peace argued that humans would be entirely made up of conflict, and the Angel of Truth argued that humans would be entirely made up of lies. In response, the Blessed Holy One flung the Angel of Truth to the earth, whereupon all the other ministering angels gathered around and said, “But Master of all the worlds, is not Truth Your own seal? Raise Truth back up from the earth!”
The Angel of Truth, of course, speaks the truth: we humans are indeed “entirely made up of lies.” Look no further than our Torah portion and then at our own experiences. We, like Rebekah, Jacob, and Isaac, are profoundly limited in our perspective, in our awareness, in our understanding of our own desires. We make assumptions about others’ motives all the time. It is not our fault that we cannot recognize the whole truth. According to the midrash, our inability to recognize the full truth is essential to the way we were created.

Rabbi Lisa L. Goldstein, "Emet- Truth, Hidden and Revealed," in The Mussar Torah Commentary, p.40
So what do we do? We bring greater attention to our habits of truth-telling and lying. When is it easy for us to tell the truth? When do we take refuge in a lie? When we find ourselves not telling the truth, we can, like Rebekah, look deeper inside ourselves and search for an explanation from our inner knowing: What is in fact the truth? Is there some truth contained within this falsehood? How might things be different if we could acknowledge that hidden truth? We humans may be “entirely made up of lies,” but we are also made in the divine image. By bringing more truth into the world, we can bring more divinity into the world and lessen suffering for us all.

Indeed, God himself, whose signature may be Truth, has moments of diplomacy. When God reports to Avraham that Sarah laughs, he changes details in the story to keep the peace between husband and wife. We see this with Moshe’s brother Aharon as well, who in rabbinic literature is the icon of mediation. Aaron, who is dubbed אוהב שלום ורודף שלום, lover of peace and seeker (literally, “chaser”) of peace, is told to have twisted the truth a bit when seeking to resolve conflicts between members of a couple.

It’s a delicate dance. A tightrope walk between אמת, truth, and חסד, kindness. May we be blessed with the patience to see the other’s point of view, the courage to be ourselves, and the wisdom to express ourselves in a way that merges the two qualities to brings about שלום, peace.

Everyday Holiness -- Alan Morinis p. 169
Truth involves not only speaking accurately, but even more important and earlier in the process, seeing accurately. And since truths are often multiple, so must be our perspectives.

Seeing a situation from the vantage point of others who are involved is one principle we need to apply to truth. Another is to be sensitive to the results that spring from our "truth."

Deborah Lipstadt, author of
"Denying the Holocaust: The Growing Assault on Truth and Memory,"
Behind the lies of Holocaust denial
TED talk Posted May 2017

...Many of us have been taught to think there are facts and there are opinions — after studying deniers, I think differently. There are facts, there are opinions, and there are lies. And what deniers want to do is take their lies, dress them up as opinions — maybe edgy opinions, maybe sort of out-of-the-box opinions — but then if they're opinions, they should be part of the conversation. And then they encroach on the facts.
...
So why is my story more than just the story of a quirky, long, six-year, difficult lawsuit, an American professor being dragged into a courtroom by a man that the court declared in its judgment was a neo-Nazi polemicist? What message does it have? I think in the context of the question of truth, it has a very significant message. Because today, as we well know, truth and facts are under assault. Social media, for all the gifts it has given us, has also allowed the difference between facts — established facts — and lies to be flattened.
...
Truth is not relative. Many of us have grown up in the world of the academy and enlightened liberal thought, where we're taught everything is open to debate. But that's not the case. There are certain things that are true. There are indisputable facts — objective truths. ... The Earth is not flat. The climate is changing. Elvis is not alive...
...
And most importantly, truth and fact are under assault. The job ahead of us, the task ahead of us, the challenge ahead of us is great. The time to fight is short. We must act now. Later will be too late.

QUESTIONS:
Are you aware of ways in which you "shade" the truth to yourself or others? Can you identify any fears that motivate you to make that choice?

Are there situations in which you habitually deceive yourself or others?

Why do people deceive themselves and others?

Why do people believe untruths?

Pause before you speak and strive to be truthful. Pause before you consume media and consider where the information came from and whether it contains bias, deception or partial truth.

Study the chapter on Truth in your favorite Mussar text. I highly recommend Everyday Holiness by Morinis for this topic.

Count the Omer after sundown.

Write for 10-20 minutes at the end of each day reflecting on Truth.

One who always wants to be victorious is very intolerant of truth. The truth may be staring him in the face. But because he is determined to win at all costs he ignores it completely. If you want to find the real truth you must rid yourself of the urge to win. Then you will be able to see the truth if you wish.

Rabbi Jonathan Sacks, The Dignity of Difference, p. 64-65
For life to be livable, truth on earth cannot be what it is in heaven. Truth in heaven may be platonic – eternal, harmonious, radiant. But man cannot aspire to such truth, and if he does, he will create conflict not peace. Men kill because they believe they possess the truth while their opponents are in error. In that case, says God, throwing truth to the ground, let human beings live by a different standard of truth, one that is human and thus conscious of its limitations. Truth on the ground is multiple, partial. Fragments of it lie everywhere. Each person, culture and language has part of it; none has it all. Truth on earth is not, nor can it aspire to be, the whole truth. It is limited, not comprehensive; particular, not universal. When two propositions conflict it is not necessarily because one is true the other false. It may be, and often is, that each represents a different perspective on reality, an alternative way of structuring order, no more and no less commensurable than a Shakespeare sonnet, a Michelangelo painting or a Schubert sonata. In heaven there is truth; on earth there are truths. Therefore each culture has something to contribute. Each person knows something no one else does.

The sages said: ‘Who is wise? One who learns from all men.” The wisest is not one who knows himself wiser than others: he is one who knows all men have some share of the truth, and is willing to learn from them, for none of us knows all the truth and each of us knows some of it. …What would faith be like? …It would be to know that I am a sentence in the story of my people and its faith, but that there are other stories, each written by God out of the letters of lives bound together in community, each bearing the unmistakable trace of his handwriting. Those who are confident in their faith are not threatened but enlarged by the different faith of others. In the midst of our multiple insecurities, we need that confidence now.

Tol'dot is a trouble portion for those who are seeking guidance on how to live an upright, ethical life; indeed, it seems more attuned to those with a Machiavellian orientation toward getting what they want. Upon first reading, Tol'dot is an account of falsehood upon falsehood, deceit upon deceit, as the members of Isaac and Rebekah's family each act for their own personal gain.
-Rabbi Lisa A. Goldstein

Middas ha'emes, truth-perception, requires the ability to perceive reality as it really is, and to live one's life based on that reality...Growth in middas ha'emes requires recognizing the illusions we may be holding onto, and discarding them.... The shedding of illusions is a lifelong struggle that, like all spiritual growth, requires one's courage to move beyond one's natural inclinations... and ultimately, to perceive the finite as thoroughly informed by the Infinite.
-Batya Gallant

This rather different interpretation of emet, which I embrace, requires us to hone our powers of observation and to listen to our hearts in addition to the "facts." It is based on the word's very composition. In Hebrew, the word emet is spelled alef-mem-tav, alef being the first letter of that alphabet, mem occupying the middle position, and tav bringing up the rear as the final letter. In short, emet embraces a "from A to Z" perspective. It encompasses the complete picture, the fullness of reality, The middah of emet asks us to assess, judge, inform, teach, speak, observe, listen, and incline all our thoughts and behavior toward acknowledgment of the fullness of life in all its complexity–as we see it and as others might see it.
-Rabbi Carol Glass

The Torah’s treatment of the topic of truth and falsehood is exquisitely sensitive. The mitzvah to “distance ourselves from falsehood” is not only a prohibition against outright verbal lies that cause direct or indirect loss to another, but includes a prohibition against any gesture or even an act of silence that results in a deceptive message being understood by the observer.

Even so, the Torah allows one to alter the truth for the sake of pursuing peace, fulfilling a mitzvah, praising a bride, and maintaining one’s humility and modesty. This leniency is only permitted where the falsehood does not affect anyone else adversely, there are no other means available, and one does not do it regularly. Finally, one who strives to be truthful in all his affairs is “walking in God’s ways” and helps to sustain the entire world.

There are those who think that maybe we should simply give up on the idea of truth altogether. After all, your truth is different than my truth, then why try to reconcile them? Indeed, truth is the beginning of conflict after conflict. “If my story is true, your story cannot be true.”

There is a story in the Midrash that tries to capture this idea. When God desired to create human beings, God convened the Heavenly court to see what was thought of the matter. Chesed, selfless love, came down on the side that humans should be created, since humans would perform acts of kindness. Emet, Truth, however, was on the opposite side. Emet said, humans are entirely lies! Then Tzedek, Justice, said humans will do acts of justice, so humans should be created. Shalom, Peace, said “do not create them, they are entirely dissension [קְטָטָה]!”

While Chesed and Tzedek focused on what humans would do in the world, Emet and Shalom focused on what the essence of humans would be. God took Emet and threw it to the Earth. While the rest of the angels continued to argue about what God should do, God went ahead and created human beings.

This is a rich midrash with many layers of interpretation. When God throws Emet to the ground, there is no Truth to argue against the creation of humans anymore. Arguing with Truth is pointless. So, one possible read of this Midrash is that in order to create we shouldn’t worry about truth. Another interpretation is that if we didn’t have truth in the world to fight about, then we would have peace – maybe we should give up the fight for truth in the world.

But in the world of Midrash, which holds the essence of Rabbinic Judaism, one cannot help but understand multiple possibilities. That’s because as soon as one understands one interpretation of a text in the midrash, there is immediately the words Davar Acher – another interpretation.

As we pursue truth that begins with science, we should also recognize that all our knowledge is always contingent. We don’t have to abandon truth simply because there exists a davar acher, another possibility. On the contrary, davar acher does not mean that there is no truth, or that there are multiple truths, rather that there are multiple perspectives to find our way to the same truth. The work of our time is to not abandon truth altogether, but to find it sprouting from the earth, and recognizing that there are multiple ways to get there. Rabbinic Judaism calls us to seek out davar acher – a different interpretation – so we can best understand the world around us.