Youcat commented through CCC – Question n. 226.

YOUCAT Question n. 226 - But we have Baptism, which reconciles us with God; why then do we need a special sacramental Reconciliation?

(Youcat answer) Baptism does snatch us from the power of sin and death and brings us into the new life of the children of God, but it does not free us from human weakness and the inclination to sin. That is why we need a place where we can be reconciled with God again and again. That place is confession. 

A deepening through CCC

(CCC 1425) "You were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and in the Spirit of our God" (1 Cor 6:11). One must appreciate the magnitude of the gift God has given us in the sacraments of Christian initiation in order to grasp the degree to which sin is excluded for him who has "put on Christ" (Gal 3:27). But the apostle John also says: "If we say we have no sin, we deceive ourselves, and the truth is not in us" (1 Jn 1:8). And the Lord himself taught us to pray: "Forgive us our trespasses" (Cf. Lk 11:4; Mt 6:12), linking our forgiveness of one another's offenses to the forgiveness of our sins that God will grant us.

Reflecting and meditating 

(Youcat comment) It does not seem like a modern thing to go to confession; it can be difficult and may cost a great deal of effort at first. But it is one of the greatest graces that we can receive again and again in our life—it truly renews the soul, completely unburdens it, leaving it without the debts of the past, accepted in love, and equipped with new strength. God is merciful, and he desires nothing more earnestly than for us, too, to lay claim to his mercy. Someone who has gone to confession turns a clean, new page in the book of his life.

(CCC Comment)

(CCC 1426) Conversion to Christ, the new birth of Baptism, the gift of the Holy Spirit and the Body and Blood of Christ received as food have made us "holy and without blemish," just as the Church herself, the Bride of Christ, is "holy and without blemish" (Eph 1:4; 5:27). Nevertheless the new life received in Christian initiation has not abolished the frailty and weakness of human nature, nor the inclination to sin that tradition calls concupiscence, which remains in the baptized such that with the help of the grace of Christ they may prove themselves in the struggle of Christian life (Cf. Council of Trent (1546) DS 1515). This is the struggle of conversion directed toward holiness and eternal life to which the Lord never ceases to call us (Cf. Council of Trent (1547): DS 1545; LG 40). 

(The next question is: Who instituted the sacrament of Penance?)