When we sin, we offend both God, and his body on earth, the church. We are forgiven as soon as we truly repent. As with any time we are repentant for offending someone, we would go to that person and say what we did, and say we are sorry. Thus we owe this to both God, and his church. Confessions allows the penitent to do this in one fell swoop, and this act fulfills the sinner’s repentance. Furthermore, in our human, doubtful nature, through it God allows us to be assured of our forgiveness and reconciliation without any doubt, and even goes so far as to give extra grace to not commit the sin again.