http://revach.net/article.php?id=3198

Section: Parshas HaShavua   Category: Life Lessons
Parshas Vayigash: Rav Chaim Shmuelevitz - Yosef's "Mussar" To His Brothers, A Real Moment Of Truth
The Medrash says, "Oy Lanu MiYom HaDin, Oy Lanu Miyom HaTochacha", woe is to us from the day of judgement, woe is to us from the day of Mussar from Hashem.  The medrash makes this statement based on the incredible embarrassment that the Shevatim felt when Yosef revealed himself to them and gave them mussar.

Rav Chaim Shmuelevitz asks (Sichos Mussar Maamar 22), where do we see that Yosef gave the brothers mussar?  All he did was reveal himself to them.  On the contrary he made a great effort to tell them it was the will of Hashem and not their own doing that caused all the event of the past 20 odd years to transpire.

Rav Chaim answers that our view of mussar is not completely accurate.  Mussar does not mean to tell someone off.  Mussar means to reveal the truth to someone who sees things through a distorted view.  Because all the persons actions are based on untruths, when he realizes his mistake and everything he did based on it, he will be very embarrassed.

The Shevatim thought they had it all figured out.  Yosef was the bad guy and they saved the future of Am Yisroel by getting rid of him for once and for all.  Life after that took many strange turns but they never second guessed their righteousness in dealing with him.  Now Yosef, in a literal moment of truth, removes the veil and brings all their mistakes to light.  All he has to do is say, "I am Yosef" and this causes them terrible embarrassment as their lifelong "Shitta" unravels in an instant.

If this is how the Shevatim HaKedoshim felt before Yosef, certainly when we live our whole lives based on mistruths that we sell ourselves, when we get to Shamayim the embarrassment will be beyond comprehension, especially since it will be too late to make amends.