God has demanded perfection from us. Repentance is both contrition and faith. Repentance is God's work. Repentance is not our work or a type of penance that we do that is acceptable to God. The Holy Spirit works through God's Law in His Word to bring us to contrition.
Contrition is sorrow for sin.
It is not just sorrow that we got caught in a sin. It is not even just sorrow that we sinned against another human being. Contrition is sorrow that we sinned against God by what we did. Repentance is God's work. The Holy Spirit works through God's Gospel in His Word to bring us to faith in Jesus Christ as our only Savior from sin.