I've heard various answers to the following question: Why does Yehuda seem to be offering up all of the brothers including Binyomin at the end of parshas Mikeitz as slaves to Mitzrayim, never to return to their father, Yaakov, and yet at the beginning of this week's parsha, he argues vociferously that Binyomin must go back to their father Yaakov, lest his life be in danger? Which is it? Is it okay if Binyomin stays in Mitzrayim as a slave with his brothers, like Yehuda argues at the end of last week's parsha? Or is it intolerable that Binyomin not return to his father, like at the beginning of Vayigash?
Rav Mordechai Yosef from Izbitz writes, in the Mei Hashiloach, that the reason for the difference between these two stances by Yehuda is that he had basically given up on himself and his brothers at the end of last week's parsha. He offered them all up as slaves to Mitzrayim, and he'd given up on all of them. But Rav Mordechai Yosef says that we must know, just like Yehuda realized moments after he'd given up hope, that no matter how undeserving we feel of Hashem's salvation from our problems, He will save us even from that place. So Yehuda strengthened himself by saying, "Even though I did something not right [by offering myself and my brothers as slaves], it's still in Hashem's power to save me." That's what he was doing in his "Vayigash eilav Yehuda."
It doesn't matter that you or I have already made many mistakes. We may feel that we are no longer deserving of Hashem's intervention in our problems at this point. Rav Mordechai Yosef is teaching us that this isn't true. Hashem wants to hear from us, and wants us to pull ourselves up by our bootstraps, as Yehuda did, and turn to and daven to Hashem for a yeshua.