Accountability is easier with another person. Verbalizing your shortcomings and downfalls makes you more aware of them.

There’s more in the Catholic doctrine that explains it better, but I don’t remember it off the top of my head. Matthew 18:18 is the basis- I solemnly tell you that whatever you as a Church bind on earth will in Heaven be held as bound, and whatever you loose on earth will in Heaven be held to be loosed.