You Can't Handle the Truth
Hezekiah said: Whence do we know that he who adds [to the word of God] subtracts [from it]? — From the verse, God hath said, Ye shall not eat of it neither shall ye touch it. (Sanhedrin 29b)
Eve added to God's words by telling the serpent that she was not even permitted to touch the tree. The serpent then pushed her into contact with the tree and told her: See, just as death did not ensue from the touch, so it will not follow from eating of it. V. Rashi a.l.
Everyone knows that Adam and Eve made a bad mistake in the Garden of Eden. But was their primary mistake eating from the fruit? No. A look at the verses (Genesis 3:8-13) reveals something much deeper:

(ח) וַֽיִּשְׁמְע֞וּ אֶת־ק֨וֹל יְהוָ֧ה אֱלֹהִ֛ים מִתְהַלֵּ֥ךְ בַּגָּ֖ן לְר֣וּחַ הַיּ֑וֹם וַיִּתְחַבֵּ֨א הָֽאָדָ֜ם וְאִשְׁתּ֗וֹ מִפְּנֵי֙ יְהוָ֣ה אֱלֹהִ֔ים בְּת֖וֹךְ עֵ֥ץ הַגָּֽן׃ (ט) וַיִּקְרָ֛א יְהוָ֥ה אֱלֹהִ֖ים אֶל־הָֽאָדָ֑ם וַיֹּ֥אמֶר ל֖וֹ אַיֶּֽכָּה׃ (י) וַיֹּ֕אמֶר אֶת־קֹלְךָ֥ שָׁמַ֖עְתִּי בַּגָּ֑ן וָאִירָ֛א כִּֽי־עֵירֹ֥ם אָנֹ֖כִי וָאֵחָבֵֽא׃ (יא) וַיֹּ֕אמֶר מִ֚י הִגִּ֣יד לְךָ֔ כִּ֥י עֵירֹ֖ם אָ֑תָּה הֲמִן־הָעֵ֗ץ אֲשֶׁ֧ר צִוִּיתִ֛יךָ לְבִלְתִּ֥י אֲכָל־מִמֶּ֖נּוּ אָכָֽלְתָּ׃ (יב) וַיֹּ֖אמֶר הָֽאָדָ֑ם הָֽאִשָּׁה֙ אֲשֶׁ֣ר נָתַ֣תָּה עִמָּדִ֔י הִ֛וא נָֽתְנָה־לִּ֥י מִן־הָעֵ֖ץ וָאֹכֵֽל׃ (יג) וַיֹּ֨אמֶר יְהוָ֧ה אֱלֹהִ֛ים לָאִשָּׁ֖ה מַה־זֹּ֣את עָשִׂ֑ית וַתֹּ֙אמֶר֙ הָֽאִשָּׁ֔ה הַנָּחָ֥שׁ הִשִּׁיאַ֖נִי וָאֹכֵֽל׃

(8) They heard the sound of the LORD God moving about in the garden at the breezy time of day; and the man and his wife hid from the LORD God among the trees of the garden. (9) The LORD God called out to the man and said to him, “Where are you?” (10) He replied, “I heard the sound of You in the garden, and I was afraid because I was naked, so I hid.” (11) Then He asked, “Who told you that you were naked? Did you eat of the tree from which I had forbidden you to eat?” (12) The man said, “The woman You put at my side—she gave me of the tree, and I ate.” (13) And the LORD God said to the woman, “What is this you have done!” The woman replied, “The serpent duped me, and I ate.”

Rashi explains:

God obviously knows what Adam has done, yet He does not attack with an accusation. Rather, God strikes up a conversation, asking in a gentle, non-threatening way: "Where are you?" He gives Adam a chance to admit his mistake, and express regret.
Instead, Adam hides and blames it all on Eve. Eve passes responsibility off to the snake. Everyone claims they did nothing wrong!
That was their worst mistake.
God knows we're not perfect ― He's the one who created us this way! But He does expect us to take responsibility for our actions and admit when we've done wrong. Because without doing so, there is no hope to correct it in the future.
Why is it that so many people have trouble admitting when they're wrong?
One possible reason is that without an absolute standard of right and wrong, there may be no compelling reason to admit wrongdoing.
Admitting guilt is out of vogue in western society. In fact, pop psychology has done all it can to remove whole concept of "guilt" from our lexicon. It's much easier to rationalize our mistakes away. And it's unhealthy to feel guilt, they say. "Suppress it!"
On one level, this suppression is unhealthy. When we refuse to admit, it is depressing and paralyzing. The regret stays inside and festers.
On another level, this suppression is downright dangerous. When one repeats an inappropriate act, he will eventually come to rationalize it as proper. Heinrich Himmler wrote that in his own personal experience with killing Jews, the turning point came when he was able to fall asleep at night without any guilt. He knew then that he'd crossed the point of no return.
In the Hebrew calendar this is the month of Elul. It is traditional for us to reflect on the past year and seek ways to improve ourselves. The ArtScroll Machzor explains:
"As an intelligent, thinking, imaginative being, man has all sorts of thoughts flashing constantly through his mind. Even sublime thoughts of remorse and self-improvement are not strange to him, but they do not last. For his thoughts to have lasting meaning, he must distill them into words, because the process of thought culminates when ideas are expressed and clarified.
"That is not as easy as it sounds. It is usually excruciatingly difficult for people to admit explicitly that they have done wrong. We excuse ourselves. We refuse to admit the truth. We shift blame. We deny the obvious. We excel at rationalizing. But the person who wrenches from himself the unpleasant truth, "I have sinned," has performed a great and meaningful act."
This lesson is crucial as we approach the High Holidays, the time when we stand in front of the mirror and see the stark reality of who we are. Maimonides explains:
"For every Mitzvah in the Torah that a person transgresses, he needs to confess before God ... What does this consist of? The person says: 'God, I have sinned before you; I have done this specific act; I am ashamed of my actions; and I will never do it again." (Laws of Teshuva 1:1)
In Judaism, confession is a totally private matter, between you and God. In fact, the Hebrew word for confession ― li-heet-vadot ― is the "reflexive" form which connotes acting upon oneself. Though we speak to God, He knows the truth already.
The problem is when we're not willing to admit the truth to ourselves. As the prophet Jeremiah says, "God will judge us when we say 'I didn't sin.'"
Incredibly, the incident of Adam and Eve occurred on the very first Rosh Hashanah, the day that humanity was born. Rosh Hashanah is thus the most opportune day to repair that mistake.