Youcat commented through CCC – Question n. 313.

YOUCAT Question n. 313 - Why must a sinner turn to God and ask him for forgiveness?

(Youcat answer)  Every sin destroys, obscures, or denies what is good; God, however, is all-good and the author of all good. Therefore every sin goes against God (also) and must be set right again through contact with him.   

A deepening through CCC

(CCC 1847) "God created us without us: but he did not will to save us without us" (St. Augustine, Sermo 169, 11, 13: PL 38, 923). To receive his mercy, we must admit our faults. "If we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just, and will forgive our sins and cleanse us from all unrighteousness" (1 Jn 8-9). (CCC 1455) The confession (or disclosure) of sins, even from a simply human point of view, frees us and facilitates our reconciliation with others. Through such an admission man looks squarely at the sins he is guilty of, takes responsibility for them, and thereby opens himself again to God and to the communion of the Church in order to make a new future possible.    

Reflecting and meditating 

(CCC Comment)

(CCC 387) Only the light of divine Revelation clarifies the reality of sin and particularly of the sin committed at mankind's origins. Without the knowledge Revelation gives of God we cannot recognize sin clearly and are tempted to explain it as merely a developmental flaw, a psychological weakness, a mistake, or the necessary consequence of an inadequate social structure, etc. Only in the knowledge of God's plan for man can we grasp that sin is an abuse of the freedom that God gives to created persons so that they are capable of loving him and loving one another.

(The next question is: How do we know that God is merciful?)