Why must I confess to a priest, when I can just talk to God?

A: The Sacrament of Reconciliation is a sacrament of healing in unity. A sacrament is a visible sign of an invisible grace. Sacramental grace in Reconciliation is a gift of God that flows through His Church and her priests. Jesus told his Apostles: “Whose sins you forgive are forgiven them, and whose sins you retain are retained” (Jn 20:23). Our bishops are the direct successors to the Apostles and, together with their priests, they share the same mission and sacramental powers given to the original Twelve. Additionally, Paul reminds us that priests are God’s ambassadors, that Jesus works through them in a special way through the sacraments to bring us His grace. Paul says of priests, “We are ambassadors of Christ, God making His appeal through us. We beseech you on behalf of Christ, be reconciled to God” (2Cor5:20).
While Jesus gave priests and bishops the authority to forgive sins, in most cases He did not also give them the ability to read minds. In order to offer sacramental absolution, it is necessary for priest-confessors to be made aware of the penitent’s sins. This typically happens through a spoken confession.
Confessions spoken aloud give the penitent the opportunity to express real contrition and to acknowledge their sin. Additionally, one requirement for absolution within the sacrament of reconciliation is true sorrow for our acts and a resolve to avoid sin in the future. Perfect contrition is when we confess out of love for God and neighbor, imperfect contrition is when we confess out of fear for our own salvation alone. God calls us to rise in love for God and others in perfect contrition, acknowledging our faults in humble need of grace. The grace we receive in Reconciliation helps us grow stronger in love and perfect contrition the more we frequent the sacrament.
Mortal sin requires this grace of the Sacrament of Reconciliation. Mortal sin breaks unity with God and others, the grace of the sacrament reconciles us with God and neighbor. Venial sin weakens our unity and also should be confessed. The Sacrament of Reconciliation also gives us the grace to strengthen us against venial sin the next time we are tempted. If venial sin is not acknowledged and confessed in our lives, it can lead to mortal sin.  
We are made body and soul. God uses the whole person both visible and spiritual to heal and restore, as He presents Himself both visible and invisible through His Church. God calls us to unity through His Church. He works through His priests in a special way to shower His gift of grace on us to help us grow in love and unity. His priests are a visible sign of His invisible presence working toward that unity in love. 

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