Catechism of the Catholic Church
No. Para. 1490: The movement of return to God, called conversion and repentance, entails sorrow for and abhorrence of sins committed, and the firm purpose of sinning no more in the future. Conversion touches the past and the future and is nourished by hope in God's mercy.
Para. 1451: Among the penitent's acts contrition occupies first place. Contrition is "sorrow of the soul and destestation for the sin committed, together with the resolution not to sin again" (Council of Trent [1551]: DS 1676).