The horror of sin, especially mortal sin
Sin is always a great evil. All sin is an infinite evil in three ways and all mortal sin is an infinite evil in a fourth way also. Everything else which we might call a “misfortune” (and which is out of our control), is God’s Will for us and is for our good. St. Paul assures us that, except for our sins, “all things work together unto the good for those who love God.” Romans, 8:28 (emphasis added). Thus, our own sins are the only true evil for us.
A person in mortal sin must strive immediately to get back into God’s grace
When a person has the tragedy of being in mortal sin, he cannot merit through anything he says or does.
Obviously, the most important thing he can do is immediately seek to get back in the state of Sanctifying Grace, by making Acts of Contrition as perfectly as possible and by sacramental Confession (if it is available without compromise). Beware of Bishop Richard Williamson’s evil advice that you should go to confession to any priest who believes in sin.
A person cannot be sure that his act of contrition is perfect enough. If the person did succeed in making a perfect act of contrition, he is then back in the state of Sanctifying Grace and can immediately begin meriting again, while he seeks to go to confession (to an uncompromising priest, as soon as one is available).
Thus, one reason for a person to continue his prayers, good works, and penances even before going to confession, is because they are meritorious if he is back in the state of grace.
But a person in mortal sin should still strive to do good, even though there is no merit
Even if the person were not back in the state of grace, he should continue praying, doing good works and doing penance, although he would not merit supernaturally for that conduct. There are five reasons to continue this conduct even while in mortal sin:
1. This conduct does good on a natural level;
2. This conduct avoids harm on a natural level;
3. This conduct enforces habits which are good on the natural level, to help us even when we cannot merit;
4. This conduct avoids harm to ourselves by avoiding the strengthening of our bad habits or making us more prone to evil which would harm us on a natural and a supernatural level; and
5. We should always act according to reason and, even when in mortal sin, our reason tells us to pray, perform good works, and do penance.
Below, we discuss each of these five reasons.
1. This conduct accomplishes good on a natural level.
Such prayers, good works, and penance set a good example, especially for those to whom he is nearest and loves the most. Does he love his friends and family? If yes, doesn’t he want to do them good even if he does not benefit from that good? Of course, he does! Love is “willing the good for another”. So, a man who loves even naturally, wills the good for those whom he loves. So, continuing his prayer, good works, and penance is a good example which does good to his loved ones. This is especially true for parents and spouses, whose very vocation involves the care of and love of others.
Nor does it suffice to merely pretend to do good so as to give good example. That pretense is a sin of dissimulation – not leading an honest life – which is a sin against the Divine Law and the Natural Law.
Further, most fakery is discovered and it does even more harm to a person if he is a fraud, especially in the good he does.
2. This conduct avoids harm on a natural level.
By contrast, the failure to pray, do good works, and do penance can scandalize others, especially those who are nearest and dearest to him. A period of such bad example from him can ruin his friends and relatives for life, even if the person himself were to return to the state of grace. Again, a parent in mortal sin might, for example, feel like a hypocrite or unworthy to pray the Rosary with his family, and thus be tempted to not do so. But it is part of his duty and part of love to show good example to his spouse and children.
3. Prayer, good works, and penance enforce habits which are good on the natural level, to help us even when we cannot merit from them.
Men are creatures of habit. Even on a natural level, it is easier for a person to later pray, do good works, and do penance meritoriously once back in the state of Sanctifying Grace, if he maintains those natural habits even while unhappily unable to merit due to mortal sin.
Even while a person is (tragically) in mortal sin, he can work on acquiring or strengthening his natural virtues, e.g., patience. Good conduct while in mortal sin can help a person acquire or strengthen those natural virtues.
4. This conduct avoids harm to ourselves by avoiding the strengthening of our bad habits or making us more prone to evil which would harm us on a natural and a supernatural level.
Further, failures to continue those good practices lets down our guard and makes us more likely to commit future sins we otherwise would not have committed.
5. Even when in mortal sin, our reason tells us to pray, perform good works, and do penance.
Our reason is our highest and most God-like part of our nature. We should always act according to this highest and best part: viz., our reason.
Our power of reason is the way God made us in His own Image.
Even on a natural level, we know God is the source of all goodness and that we owe Him worship and prayer.
Even when in the state of mortal sin, a person’s reason tells him to pray, perform good works, and do penance as a matter of justice to God.
He owes this to God even if he does not merit from this worship and prayer. This debt to God is right and reasonable. A person must pay his debt to God even if he were not to merit, just as a child must show respect for his parents, keep his room neat, and do his schoolwork even though he did not receive a reward for doing so. Thus, reason tells a person that he must pray even if he is in mortal sin.
A person’s reason tells him to continue doing good works – they are a natural good and a man in mortal sin should follow his reason doing good works even when he cannot merit supernaturally from those good works.
Even on a natural level, we know that we must conform our lower passions to our reason and our will, and that this task requires that we mortify our passions and do penance.
Committing mortal sin is a “wake-up call” which should immediately cause us to increase our prayers and good works.
Not only should a person not stop praying and doing good works following commission of a mortal sin, but he should immediately increase his prayers and good works.
His sin is a reminder of his weakness. The best remedy for this weakness is prayer. When a person sins, it is unreasonable (and is a further sin) to not take concrete means to avoid similar falls in the future. So, the more “wake-up calls” (i.e., sins) a person commits, the more he should realize his need for more prayer – and take those means.
Sin is the only true evil. Mortal sin is the gravest evil and destroys a person’s ability to merit. However, even a man in mortal sin should continue his prayers, good works, and penances, to avoid further harm to himself and others and to make it easier to do good in the future.
 Here is how St. Alphonsus de Liguori, Doctor of the Church, teaches this truth:
A single venial sin is more displeasing to God than all the good works we can perform.
Uniformity with God’s Will, §6.
Here is how St. John of the Cross, Doctor of the Catholic Church, teaches this truth:
Our Lord said in the Gospel: “He that is unfaithful in little will be unfaithful also in much.” For he that avoids the small sin will not fall into the great sin; but great evil is inherent in the small sin, since it has already penetrated within the fence and wall of the heart; and as the proverb says: Once begun, half done.
Ascent of Mount Carmel, Book III, ch.20, section 1.
Here is how Cardinal Newman compares the smallest sin to the greatest human suffering:
The Catholic Church holds it better for the sun and moon to drop from heaven, for the earth to fail, and for all the many millions on it to die of starvation in extremest agony, as far as temporal affliction goes, than that one soul, I will not say, should be lost, but should commit one single venial sin, should tell one willful untruth, or should steal one poor farthing without excuse.
Apologia Vita Sua, by John Henry Cardinal Newman, Image Books, Doubleday, Garden City, New York, © 1956, p.324.
 Read the explanation of this truth here:
 Read the explanation of this truth here:
 The Catholic Encyclopedia teaches:
Perfect contrition, with the desire of receiving the Sacrament of Penance, restores the sinner to grace at once. This is certainly the teaching of the Scholastic doctors (Peter Lombard in P.L., CXCII, 885; St. Thomas, In Lib. Sent. IV, ibid.; St. Bonaventure, In Lib. Sent. IV, ibid.).
Catholic Encyclopedia, 1908, Volume 4, article: Contrition, page 339.
After this first attempt at a perfect act of contrition, he should continue to attempt to make further perfect acts of contrition.
Regardless of the state of his soul, everyone should strive greatly, every day, to make perfect acts of charity and perfect acts of contrition for his past sins. A man in mortal sin should do this even more urgently.
Read this article about making perfect acts of contrition:
 Read these two articles about avoiding compromise confessions:
 Read an explanation of the evil of his advice here:
 Of course, he is still obliged to go to confession when he has the chance to do so, to an uncompromising priest.
 Here is how St. Thomas Aquinas, greatest Doctor of the Church, explains this truth:
According to the Philosopher (Ethic. viii, 2,3) not every love has the character of friendship, but that love which is together with benevolence, when, to wit, we love someone so as to wish good to him. If, however, we do not wish good to what we love, but wish its good for ourselves, (thus we are said to love wine, or a horse, or the like), it is love not of friendship, but of a kind of concupiscence. For it would be absurd to speak of having friendship for wine or for a horse.
Summa, IIa IIae, Q.23, a.1, sed contra and respondeo (emphasis added).
 Summa, Ia, Q.93, a.2, found here:
 Summa, Ia IIae, Q.109, a.3.