Repairing Sin's Damage
Penance is closely connected with reconciliation. Reconciliation with God, with oneself and with others implies overcoming that radical break which is sin. And this is achieved only through the interior transformation or conversion which bears fruit in a person's life through acts of penance ....
Sacred Scripture speaks to us of this reconciliation, inviting us to make every effort to attain it. But Scripture also tells us that it is above all a merciful gift of God to humanity. The history of salvation ... is the wonderful history of a reconciliation: the reconciliation whereby God, as Father, in the blood and the cross of his Son made man, reconciles the world to himself. He thus brings into being a new family of those who have been reconciled.
Reconciliation becomes necessary because there has been the break of sin from which derive all the other forms of break within man and about him. Reconciliation, therefore, in order to be complete necessarily requires liberation from sin, which is to be rejected in its deepest roots. Thus a close internal link unites conversion and reconciliation. It is impossible to split these two realities or to speak of one and say nothing of the other.
from Breakfast with the Pope 120 Daily Readings―Pope John Paul II #34