"An awareness of our failings is a healthy antidote against over-confidence"

"Repentance does not erase our past life, nor does forgiveness erase our memory of those times we have failed to love God with all our heart, mind and soul. In point of fact, the greater our union with God, the clearer we see our entire existence. That greater union can, to some extent, come about as an effect of healthy regret. Therefore regret is not harmful or inappropriate, for it can be the result of an infusion of actual grace which moves us toward a deeper repentance and conversion, and which urges us to seek sacramental confession. Too, an awareness of our failings is a healthy antidote against over-confidence and an incorrect reliance on ourselves as opposed to placing our trust in God.

Nevertheless, regret is a feeling. The grace of forgiveness attained through the sacrament of Penance and Reconciliation is certain, provided one has made a proper confession. It is this truth and the rest of it, the fullness of truth which has now been transmitted by the Catholic Church for twenty-centuries, that drew St. Augustine away from the heretical teaching of the Manicheans toward the unsurpassable beauty of the consummation of God's revelation: the Person of Jesus Christ".

See catholic.org