Act of Contrition

O my God, I am heartily sorry for having offended Thee, and I detest all my sins because of thy just punishments, but most of all because they offend Thee, my God, who art all good and deserving of all my love. I firmly resolve with the help of Thy grace to sin no more and to avoid the near occasion of sin. Amen.

(A traditional version)

or:

My God,
I am sorry for my sins with all my heart.
In choosing to do wrong
and failing to do good,
I have sinned against you
whom I should love above all things.
I firmly intend, with your help,
to do penance,
to sin no more,
and to avoid whatever leads me to sin.
Our Savior Jesus Christ suffered and died for us.
In his name, my God, have mercy.

(from the Rite of Penance)

or:

Lord Jesus, Son of God,
have mercy on me, a sinner.

(from the Rite of Penance)