"If we say openly that we have done wrong, he is upright and true to his word, giving us forgiveness of sins and making us clean from all evil"
1 John 1:9
All sin is against God, when I admit sin (agree with God), confess, He forgives me. Without confession there is no forgiveness of sin. He doesn't beat me up over my sin, but forgives when I admit it, and His blood cleanses me from all unrighteousness, and that it ultimately removes even the stain of sin..
—Barnes' Notes on the New Testament:
"we may have the fullest assurance that God is ready to pardon us if we exercise true repentance and faith. No one can come to God without finding him ready to do all that is appropriate for a God to do in pardoning transgressors; no one who will not, in fact, receive forgiveness if he repents, and believes, and makes confession; no one who will not find that God is just to his Son in the covenant of redemption, in pardoning and saving all who put their trust in the merits of his sacrifice"