Why are we called in 'The Lord's Prayer' to ask for what appears to be additional forgiveness? One, because sin destroys. Confession helps our soul heal from the guilt we incurred. Two, because every sin we commit, though it does not forfeit our salvation, breaks fellowship with our heavenly Father. Three, because our forgiveness came at a great cost - the death of God's very Son. Therefore we ought to take sin seriously and carefully recognize the specific areas we are falling short. Four, because true believers are committed to repentance. Confession of sin is important because without acknowledging the error of sin, we will never take the necessary steps toward what God ultimately desires, which is repentance (turning from the sin altogether).