The Sacrament of Reconciliation is necessary for the forgiveness of any mortal sin.  All sin is against charity--the love of God.

The Sacrament consists of three things:

1. Contrition on behalf of the penitent.  One must make an examination of conscience with knowledge of the 10 Commandments; reference to the Beatitudes in Mt 5 and Lk 11.  Reviewing  one of the Pauline letters such as Galatians 5 to understand sins to avoid and the fruits of the Holy Spirit.  Contrition is sorrow of soul and detestation for the sin committed, together with the resolution not to sin again.  Perfect contrition arises from a love by which God is loved above all else. Imperfect contrition is also a gift of the Holy Spirit. It is born of consideration of sin's ugliness or the fear of eternal damnation.  This stirring of conscience, under the prompting of grace, is the beginning of conversion to dispose one to obtain forgiveness in this sacrament. 

2. Confession of sins and Absolution:  the penitent who is sorry for his sins, admits the sins, takes responsibility for them, and opens himself again to God and to the communion of the Church.   The priest, through the Power of the Holy Spirit offered in Holy Orders, offers absolution to remove the sin.

3. Satisfaction is to make amends by the penitent.  Many sins wrong our neighbor.  One must do what is possible in order to repair the harm: make restitution for stolen good, restore reputation of others; compensation for injury.  Absolution removes sin, and satisfaction implies doing the good afterwards.  The sinner must still recover and return to full spiritual strength by doing or praying something to make amends for the sin.  These holy actions are a response to the grace given in the sacrmament.