"Those who approach the sacrament of Penance obtain pardon from God's mercy for the offense committed against him, and are, at the same time, reconciled with the Church which they have wounded by their sins and which by charity, by example, and by prayer labors for their conversion." CCC 1422
From a letter by Saint Maximus the Confessor, abbot excerpted from The Liturgy of the Hours
… Christ proclaimed that he had come to call sinners to repentance, not the righteous and that it was not the healthy who required a doctor, but the sick. He declared that he had come to look for the sheep that was lost and that it was to the lost sheep of the house of Israel that he had been sent. Speaking more obscurely in the parable of the silver coin, he tells us that the purpose of his coming was to reclaim the royal image, which had been coated with the filth of sin. “You can be sure there is joy in heaven’, he said, over one sinner who repents.