Conversion means change. But when we’re converted, we don’t immediately appreciate the thoroughgoing nature of divine grace—that God works in and through us despite our shortcomings. So change can be slow and arduous, especially if you were raised in a religious tradition that strongly emphasizes the role of human merit.
About this experience, I can speak most specifically from my own background, which happens to be Roman Catholic. Like many who convert to Christ and begin worshiping in an evangelical Protestant context, I quickly realized the profound influence that the Catholic vision of salvation exerted upon my religious mind. For instance, perhaps the most common and spiritually injurious issue is the problem of religious guilt. It’s a nagging fear that preoccupies the soul, a root of doubt that questions whether we are truly forgiven in Christ. In bed at night I would often wonder, Has my behavior been good enough to merit divine approval? Like Martin Luther who sought a gracious God, I never knew whether I had produced a sufficient amount of righteousness to be fully accepted.
Throughout his writings, Luther describes his struggle to please God with the German word Anfechtungen. The English language lacks an adequate translation. Sometimes it is rendered "temptation" or "challenge," but in Luther’s experience Anfechtung included the existential torment of his soul and conscience. Perhaps it is best to let Luther describe it. About his days in the Catholic monastery, he writes:
I was a devout monk and wanted to force God to justify me because of my works and the severity of my life. I was a good monk, and kept the rule of my order so strictly that I may say that if ever a monk got to heaven by his monkery, I would have gotten there as well. All my brothers in the monastery who knew me will bear me out. If I had kept on any longer, I would have killed myself with vigils, prayers, reading, and other works. 
Psychology of Religious Guilt
The following anecdote is admittedly exaggerated, but the extremes can help us appreciate the deficiencies of certain views.
Imagine: You are a Catholic having dinner at Spark’s Steakhouse in New York on a Friday night. Since it’s during the season of Lent, beef of any kind is prohibited. Your host insists that you have the steak tenderloin with mustard-cognac sauce, because it’s the chef’s specialty. What do you do?
At once, your conscience sends you into a tailspin. To consider eating meat on a Lenten Friday is a venial sin, and wantingto eat it is another one. You haven’t opened the menu, and you’ve already committed two sins. Your waiter delivers your beverages and says that he will return in a moment for your order. In the meantime, you wonder, What if I ask for the steak? Would this constitute a venial or mortal sin? It all depends. If you think it’s mortal, it may very well be. If you think it’s venial, it could still be mortal.
By this point the waiter returns. He greets the host by name, looks at you, and with a genteel-sounding accent says, "May I suggest the steak tenderloin with mustard-cognac sauce?" You quickly decide that on this occasion at least, eating steak can’t be more than a venial sin, and therefore respond, "I’ll try it." Although you freely made this choice, you figure you can go to confession within 24 hours before the Saturday-evening Mass. But does a venial sin become mortal when it’s freely chosen? That’s the risk you’re taking. What if you mistakenly thought it was Thursday instead of Friday? This would allow you to eat meat; but, unfortunately, forgetting it was a Friday of Lent might be a sin. How about if you remembered it was Friday after your second forkful? Is it a venial sin to continue eating? If you fain a stomachache and not finish it, would lying then be a sin? Within ten minutes you’ve committed so many sins that your visit to purgatory has been extended by 15 years.
We understand, of course, that injurious forms of religious guilt are not limited to Catholics (although in my humble opinion, the Catholic Church is especially vulnerable to the problem). Misdirected guilt is a human problem that plagues every religious tradition, including Protestantism. In its most acute form, this guilt is not simply an incident; it is a lens through which we view the Christian faith. Over time, it can control our mental framework.
I was recently reading the humorous book Growing Up Catholic. Written by several Catholic authors, it contains a segment called "The Great Guilt Contest: The Catholics and the Jews." Maybe because I’m a Long Islander who grew up with a multitude of both, I resonate with the following excerpt. Regardless of where you’re from, you’ll find that it contains an insight concerning the problem of guilt:
In the contest for the Guilt Championship of the World, the undisputed co-champions are the Catholics and the Jews. Protestant work-ethic guilt, while a contender, just isn’t in the same league. Although Catholic guilt and Jewish guilt may appear to be similar, they actually have very different origins. Jewish guilt is generally induced by the Jewish family after the violation of a cultural tradition, such as refusing to take home the extra chicken soup your mother made for you, or becoming a forest ranger instead of a doctor.
Catholic guilt may be related to family disapproval as well, but not in such an immediate sense. The root of all Catholic guilt is the knowledge that every sin committed—past, present, or future—adds to Jesus’ suffering on the cross. Since virtually anything you do (or don’t do) may be a sin, this is a very heavy burden to bear. It’s bad enough that you have to pay for sins yourself, but making the Nicest Guy Ever take the rap also is just too awful.
Thus the two outstanding forms of guilt may be summed up as follows. The wayward Jew thinks, "What an awful thing to do to somebody." The Catholic sinner thinks, "What an awful person I am." 
When we feel awful about ourselves, our first inclination will be to hide from God. Like Adam and Even in the Garden, we sense our inadequacy seek to run from the divine presence. However, rather than fleeing, liberation comes when we turn directly toward God in repentance and faith.
Escaping the Trap
Victory over unhealthy guilt follows from understanding who we are in Christ. After several years of walking with Jesus, God used Galatians 2:20 to instill this lesson, particularly the words, "It is no longer I who live, but Christ who lives in me." Furthermore, a lesson from the ministry of Luther called the "dung hill" also allayed my troubled conscience. Maybe you’ll find it helpful too.
Supposedly, Martin Luther was sitting down with some of his students beside a window when snow started to fall. Luther pointed to a pile of manure near his house and explained to students that on account of sin the moral condition of humans resembles the stinking pile of dung. Among the implications of this condition are guilt and condemnation before God.
Within the hour snow had fallen so steadily that the dung hill was completely covered. Luther paused from his lesson and once again pointed to the mound. He asked the students to tell him what they saw. Instead of manure the students described a powdery white hill. As the sunlight gleamed off the fresh snow, Luther stated, "That is how God sees us in his Son, Jesus Christ. While we remain full of sin, in Christ we are clothed with his perfect righteousness and therefore we are acceptable in God’s sight."
Whenever I share this anecdote, I quickly point its flaws. Because God provides his Holy Spirit and accomplishes his work of sanctification in us, he makes us more than dung (feel free to say "amen"). This is where the analogy breaks down most obviously. But there’s another part of the illustration that is not only accurate, it is also glorious. It is the "great exchange": namely, Christ takes our sin and gives us his righteousness. The idea is summarized nicely by the 16th-century English theologian Richard Hooker:
Such we are in the sight of God the Father, as is the very Son of God himself. Let it be counted folly or frenzy or fury or whatsoever. It is our wisdom and our comfort; we care for no knowledge in the world but this, that man has sinned and God has suffered; that God has made himself the sin of men, and that men are made the righteousness of God. 
Because our identity is founded in the resurrected Christ seated at God’s right hand, God looks upon us as being clothed with the perfection of his Son. On this basis, we have the audacity to lift our eyes to heaven in the absence of guilt and know that we are accepted as sons and daughters of almighty God.
 Walther von Loewenich. Martin Luther: The Man and His Work. Trans. Lawrence E. Denef. (Minneapolis: Augsburg, 1982), 72.
 Mary Jane Frances Cavolina Meara, Jeffrey Allen Joseph Stone, Maureen Anne Teresa Kelly, and Richard Glen Michael Davis. Growing Up Catholic. (Garden City, New York: Dolphin Book, 1984), 123-124.
 Richard Hooker. ‘Sermon on Habakkuk 1:4‘ (1585), in The Works of Richard Hooker, ed. John Keble, vol. III (Oxford, Oxford University Press, 5th ed. 1865), 490-91.