From Pope St. John Paul II’s Apostolic Exhortation Reconciliatio et Pænitentia (1984):
There remains to be made a brief mention of other important convictions about the sacrament of penance.
First of all, it must be emphasized that nothing is more personal and intimate than this sacrament, in which the sinner stands alone before God with his sin, repentance and trust. No one can repent in his place or ask forgiveness in his name. There is a certain solitude of the sinner in his sin, and this can be seen dramatically represented in Cain with sin “crouching at his door,” as the Book of Genesis says so effectively, and with the distinctive mark on his forehead;190 in David, admonished by the prophet Nathan;191 or in the prodigal son when he realizes the condition to which he has reduced himself by staying away from his father and decides to return to him.192 Everything takes place between the individual alone and God. But at the same time one cannot deny the social nature of this sacrament, in which the whole church—militant, suffering and glorious in heaven—comes to the aid of the penitent and welcomes him again into her bosom, especially as it was the whole church which had been offended and wounded by his sin. As the minister of penance, the priest by virtue of his sacred office appears as the witness and representative of this ecclesial nature of the sacrament. The individual nature and ecclesial nature are two complementary aspects of the sacrament which the progressive reform of the Rite of Penance, especially that contained in the Ordo Pænitentiæ promulgated by Paul VI, has sought to emphasize and to make more meaningful in its celebration.
Second, it must be emphasized that the most precious result of the forgiveness obtained in the sacrament of penance consists in reconciliation with God, which takes place in the inmost heart of the son who was lost and found again, which every penitent is. But it has to be added that this reconciliation with God leads, as it were, to other reconciliations which repair the breaches caused by sin. The forgiven penitent is reconciled with himself in his inmost being, where he regains his own true identity. He is reconciled with his brethren whom he has in some way attacked and wounded. He is reconciled with the church. He is reconciled with all creation.
As a result of an awareness of this, at the end of the celebration there arises in the penitent a sense of gratitude to God for the gift of divine mercy received, and the church invites the penitent to have this sense of gratitude.
Every confessional is a special and blessed place from which, with divisions wiped away, there is born new and uncontaminated a reconciled individual—a reconciled world!
190 Cf Gn 4:7, 15.
191 Cf 2 Sm 12.
192 Cf Lk 15:17-21.
— Reconciliatio et Pænitentia 31