We see from this parsha, says the Sefas Emes, that Yehudah was able to completely put aside his own self interest and engage in fighting for Binyamin just to do what is right by Ya’akov. The old Yehudah who could not let the threat of Yosef’s dreams pass is a personality of the past. It started to vanish when rather than protect his own reputation, he acknowledged that Tamar’s children were his own; it ended here with a speech demonstrating complete selflessness.
This selflessness is what eliicited Yosef's revealing of himself. The Sefas Emes doesn't spell it out, but I think the connection is clear: so long as the brothers were acting in any way to protect and/or serve their own interests, Yosef could remain in hiding, protecting his own interests and identity as well. But when Yehudah stepped forward and acted without any personal negiyos, purely out of empathy for the pain of another, Yosef was forced to respond in kind and abandon his personal hope of his dreams being completely fulfilled and instead, overcome by empathy for their brother's pain, he was forced to reveal himself.
2) We finally come to the conclusion of the drama of Yosef and his brothers, and instead of simchas torah it seems like tisha b’av. “He fell on the neck of his brother Binyamin and cried and Binyamin cried on his neck.” (45:14) Rashi comments that Yosef cried because he foresaw the destruction of the Mikdash, which was built in Binyamin’s portion, and Binyamin cried for the destruction of the Mishkan, which was built in Yosef’s portion.
Why were the brothers crying over the destruction of the Mikdash and Mishkan in what should have been a joyous moment of their reunification?
The Sefas Emes explains that the tragedy of galus came about because there rift between the brothers was not in fact fully healed. Yosef wanted to hold out longer to achieve a complete tikun, but he could not. Yosef and Binyamin therefore cried over the future churban that they knew would inevitably result.
3)Chazal draw a kal v’chomer: if the brothers were so taken aback with shame and remorse when Yosef revealed himself, how much more filled with shame and embarrassment will we be on the day of G-d’s judgment.
The Sefas Emes points out that this is not just some arbitrary comparison, but rather there is an underlying common denominator. Yosef’s revelation proved that all that the brother’s had perceived on the surface –- that they were dealing with some Egyptian viceroy who was playing games with them – was false. It was really Yosef, it was really hashgacha, it was really l’tovah. On the future day of judgment G-d is going to show us that everything in life that we see as negative, as an obstacle to growth, as devoid of kedudah, is really just a disguise, and beneath it all was hashgacha, was tovah, was bracha. G-d is not going to shower the world with new kedusha; He is just going to show us the kedusha that was always immanent. And then we are going to kick ourselves for not seeing it that way earlier.
(This is a theme that runs through the Sefas Emes; I think you can probably find it in every parsha. Spirituality is not "out there" somewhere, seperate from the day-to-day reality of life, but is already inside, b'pnimiyus. It just has to be revealed.)