Question:
Lately I have been having a lot of confusion trying to figure out if and how G-d can forgive people of their sins. Suppose someone sins by killing another person or setting someone's house on fire, and then that person genuinely repents and desires to do all that he/she can to repair the damage. Suppose G-d and also the victims of the sin forgive the sinner. But the person who was killed is still dead and the house burnt still needs to be built! How can the person be forgiven if the effects of his or her crime still exist?
Answer:
Much of your quandary arises from confusing two related issues: forgiveness and healing.
If one of my children would spill red paint from her social studies project all over the living room carpet and them come crying to me, saying, "Daddy, I made a big mistake! I feel so bad!" --I would probably forgive her pretty fast. But I would still ask her to clean up the paint.
Which means: I haven't held out on forgiving her until she cleaned up the mess. I've forgiven her entirely. It's just that it's her mess, so she has to clean it up.
So, too, whenever a person messes up in this world, it causes damage to the world, to the soul and to the body. A Jew may spend the first fifty years of her life eating non-kosher food, so that every cell of her body is made of a substance that imprisons the Jewish soul. In one moment, she may regret and ask forgiveness--and she will be completely forgiven. But now she must be careful to keep the kosher laws so that all those cells be changed over to kosher ones.
We call this "tikkun", which means repair--a type of healing of the soul, the body and the world. Not always can it be achieved in a single lifetime. We may have to return again and again until the tikkun is achieved. A tzaddik can often assist a person to find the proper tikkun for specific sins. But, as I said, the first step is to feel true regret and determine to abandon the sin altogether. That alone is enough to procure forgiveness.