In our secular humanistic culture, many people, even Christians, have unformed and deformed consciences. They have not been "trained by practice to distinguish good from evil" (Heb 5:14). "One sees in them men without conscience, without loyalty, without affection, without pity" (Rm 1:31). These people commit many serious sins, but do not feel guilty because they are so spiritually blinded and immature.
However, this condition of serious sin, minimal guilt, and undeveloped consciences will not last indefinitely. Reality finally sets in, and they come to realize that they have sinned grievously. At this point, the guilt that has been dammed up for years floods them. They feel more guilty in one week than they have in their whole lives. They feel doomed, hopeless, and hell-bound, when previously they hardly even thought about there being a hell. Overwhelmed and nearly crushed by guilt (see Hos 14:2), they cry out to the Lord. He forgives, frees, and heals them by assuring them: "Though your sins be like scarlet, they may become white as snow; though they be crimson red, they may become white as wool" (Is 1:18).
There is hope and healing for the guilt-ridden. On Calvary, Jesus took our sins and guilt on Himself (Is 53:5-6). Therefore, we can be thoroughly washed from guilt and cleansed from sin (Ps 51:4). Thank You, Jesus.