Chapter 19 — Part II: The Sacraments — Penance
Section 11. Meaning Of Penance — Interior penance consists in turning to God sincerely and from heart, and in hating and detesting our past transgressions, with a firm resolution of amendment of life, hoping to obtain pardon through the mercy. Accompanying this penance, like inseparable companion of detestation for sin, is a sorrow and sadness, which is a certain agitation and disturbance of the soul, and is called by many a passion. Hence many of the Fathers define penance as an anguish of soul.