"Penance is the sacrament of Christ's Precious Blood in which God- according to the eloquent words of Saint Catherine of Siena- "has bathed us in order to cleanse the face of our souls from the leprosy of sin." If mortal sin is only the necessary matter of this sacrament, venial sin is sufficient matter, since al  Catholic tradition insists on frequent confession, even when one has only venial sins to confess. However, those who confess weekly must take great care lest their confessions become a mere routine, instead of the really vital acts which would enable these souls to profit fully from all the graces offered by the sacrament." Divine Intimacy