From Pope St. John Paul II’s Apostolic Exhortation Reconciliatio et Pænitentia (1984):
The pastors of the church are also expected to provide catechesis on penance. Here too the richness of the biblical message must be its source. With regard to penance this message emphasizes particularly its value for conversion, which is the term that attempts to translate the word in the Greek text, metanoia,138 which literally means to allow the spirit to be overturned in order to make it turn toward God. These are also the two fundamental elements which emerge from the parable of the son who was lost and found: his “coming to himself”139 and his decision to return to his father. There can be no reconciliation unless these attitudes of conversion come first, and catechesis should explain them with concepts and terms adapted to people’s various ages and their differing cultural, moral and social backgrounds.
This is a first value of penance and it extends into a second: Penance also means repentance. The two meanings of metanoia appear in the significant instruction given by Jesus: “If your brother repents (returns to you), forgive him; and if he sins against you seven times in the day, and turns to you seven times and says, ‘I repent,’ you must forgive him.”140 A good catechesis will show how repentance, just like conversion, is far from being a superficial feeling but a real overturning of the soul.
A third value is contained in penance, and this is the movement whereby the preceding attitudes of conversion and repentance are manifested externally: This is doing penance. This meaning is clearly perceptible in the term metanoia, as used by John the Baptist in the texts of the synoptics.141 To do penance means above all to restablish the balance and harmony broken by sin, to change direction even at the cost of sacrifice.
A catechesis on penance, therefore, and one that is as complete and adequate as possible, is absolutely essential at a time like ours when dominant attitudes in psychology and social behavior are in such contrast with the threefold value just illustrated. Contemporary man seems to find it harder than ever to recognize his own mistakes and to decide to retrace his steps and begin again after changing course. He seems very reluctant to say “I repent” or “I am sorry.” He seems to refuse instinctively and often irresistibly anything that is penance in the sense of a sacrifice accepted and carried out for the correction of sin. In this regard I would like to emphasize that the church’s penitential discipline, even though it has been mitigated for some time, cannot be abandoned without grave harm both to the interior life of individual Christians and of the ecclesial community and also to their capacity for missionary influence. It is not uncommon for non-Christians to be surprised at the negligible witness of true penance on the part of Christ’s followers. It is clear, however, that Christian penance will only be authentic if it is inspired by love and not by mere fear; if it consists in a serious effort to crucify the “old man” so that the “new” can be born by the power of Christ; if it takes as its model Christ, who though he was innocent chose the path of poverty, patience, austerity and, one can say, the penitential life.
138 Cf Mk 1:14; Mt 3:2; 4:17; Lk 3:8.
139 Cf Lk 15:17.
140 Lk 17:3f.
141 Cf Mt 3:2; Mk 1:2-6; Lk 3:1-6.
— Reconciliatio et Pænitentia 26