Mercy can penetrate our hearts only if we ourselves learn how to forgive–even our enemies. Now even if it seems impossible for us to satisfy this requirement, the heart that offers itself to the Holy Spirit can, like Christ, love even to love’s extreme; it can turn injury into compassion and transform hurt into intercession. Forgiveness participates in the divine mercy and is a high-point of Christian prayer.

-Compendium of the Catechism of the Catholic Church, # 595