Jon Walker in his book, In Visible Fellowship: A Contemporary View of Bonhoeffer’s Classic Work:  Life Together writes in chapter 31 about how confession is a break-through to the cross, Dietrich Bonhoeffer wrote…

The cross of Jesus Christ destroys all pride. We cannot find the Cross of Jesus if we shrink from going to the place where it is to be found, namely, the public death of the sinner. And we refuse to bear the Cross when we are ashamed to take upon ourselves the shameful death of the sinner in confession.

Walker writes that The Big Idea of the chapter is…

Often, when we sin, our pride steps in the way and tells us not to do it. And this just adds to the sin of pride we’ve stuffed in the shadows. Confessing to another breaks our pride because it is painful and humiliating, but it is also the very thing that brings us back to the Cross of Christ, where he suffered pain and humiliation because of our sin.

Walker added:

Isn’t it funny how we are often more willing to tell our sins to God than we are to confess them to another person. And that is precisely why the Bible teaches us to confess our sins to one another. 

It forces us to bring our sin out of the abstract and general into the concrete and specific. It forces us to face the truth that our sin is powerful enough to destroy our fellowship with Jesus and with one another, but it also reminds us that God’s grace is greater than our sin, that Jesus spilled his blood to bring us back into fellowship with the Father–and connect us together, accepted into God’s beloved family. 

(Jon WalkerIn Visible Fellowship: A Contemporary View of Bonhoeffer’s Classic Work: Life Together, Chapter 31)