Our Gemara on Amud Beis discusses the halakhic principle that if one who admits he is liable to pay a fine, than he is exempt from actually having to pay it. This pardoning applies even if, after his admission, witnesses come forward with independently valid testimony that would have convicted him.

The Shalah (Aseres HaDibros, Yoma, Torah Ohr 23) understands this as true metaphysically in relation to sin and God’s punishment. The power of confessing sins (in Judaism this can be quietly verbalized to oneself) acts to forestall punishments from the Heavenly Court as well. 

Even psychologically speaking, self-honesty is critical to growth and self-esteem. Facing one’s flaws, fears, and distorted sense of entitlement is the first and critical step in being able to change personality traits that interfere with healthy relationships. Confession that comes from deep realization and awareness has the power to bring about significant personal development.