If we insult a friend, it is our duty to ask his pardon, to tell him we are sorry, to promise that we shall not repeat the offense. We must do the same toward God when we offend Him by sin. We cannot expect Him to forgive us unless we turn to Him with true sorrow of soul, or contrition. On the other hand, if we turn to Him with the necessary contrition, He will forgive us. In this, His mercy is greater than that of creatures. Sometimes we ask a human being to pardon the wrong we have done, but he refuses. But God is always ready to forgive the sinner, however wicked he has been, if he returns to his heavenly Father with true sorrow of heart. Naturally, this sorrow must be based on motives of faith, not on merely natural motives. It must extend to all mortal sins, it must include a firm purpose of not sinning, at least mortally, in future; it must contain the will to endure any suffering rather than offend God by grievous sin in the time to come. Such an act of contrition is not difficult for any one who knows from the principles of the Catholic faith how terrible an evil is sin One must remember also that God is always ready to give the grace to make an act of contrition to any one who sincerely begs His assistance.
When we say that God will not forgive any sin without contrition, we are speaking only of actual sin, not of original sin. We cannot have contrition for original sin since we did not contract it by our own free will; hence, infants who have only original sin are cleansed of that sin by Baptism, without making any act of contrition.
In the sacrament of Penance, contrition based on any supernatural motive suffices, even though it arises merely from the fear of God's punishments, of which He has spoken to us frequently in revelation. It is true, contrition based on fear alone is not very noble. Indeed, it might be called selfish. Yet, Our Lord proposed this as a good motive of contrition when He said: "Be afraid of him who, after He was killed, has power to cast into hell" (Luke, 12: 5). Other reasons for contrition, sufficient to obtain the forgiveness of sins in the sacrament of Penance, are the realization of the ingratitude to God that every sin contains, the hatefulness of sin as opposed to the supernatural virtues, the injustice to our Creator included in every transgression of His law.
The most noble type of contrition is that which arises from the love of God for His own sake, or because of His own goodness. This is called perfect contrition, and it has the power to procure the forgiveness of all mortal sins that may be on the soul of the person who detests his sins from this motive. It was of this contrition that Our Lord spoke when He said, pointing to the repentant sinner, Mary Magdalen, "Her sins, many as they are, shall be forgiven her, because she has loved much" (Luke, 7: 47). It is indeed unfortunate that Catholics are often unaware of the wonderful power of perfect contrition. Some think it remits sin only when one is in danger of death and cannot get to confession. The truth is that an act of perfect contrition will always take away mortal sin; one has only to have the intention of going to confession when he is next obliged to do sothat is, within the year or when in danger of deathand telling the mortal sins which have been remitted by perfect contrition. One who has had his sins forgiven by perfect contrition may not go to Communion until he has been to confession; nevertheless he can enjoy the advantages of being in the state of grace and of gaining merit for his good works.
A person can have at the same time both perfect and imperfect contrition for his sins. One does not exclude the other. For this reason we say in our act of contrition: "I detest all my sins because of thy just punishments" thus expressing imperfect contrition, and then we add our expression of perfect contrition, when we say: "But most of all because they offend Thee, my God, who art all good and deserving of all my love."