Actually, that's not why one forgives. One forgives only when reparation is made. That was both so in the Jewish tradition and the early Christian tradition. When Jesus was asked how many times one should ask someone for forgiveness, the answer was that as many times as it took for the person to forgive one.
The context of that question was that God would not forgive one until the person whom one had wronged had forgiven one, and reparation to the wronged person was an essential part of forgiveness.
Forgiveness means to put things back to the way they were. It means to make the the playing fields level again. It has nothing to do with forgiving others so that one feels better.
I don't care why people do evil things. In all my pain and hell, I never, never, never did bad things. Some people are just born jerks, and others are born good. You can check that one in the bible as well.
In the days when I studied the bible, there was a verse that fascinated me. It was in one of the epistles. It said that some were created by god to burn in hell for eternity - that these things were predestined.
I, of course, don't believe any of this, but as you are coming to me with something that is taught by fundamentalist Christianity, I am responding with the things that would make more sense to you.
If you want a correct translation/interpretation of the forgiveness, this is my book that covers it (amongst other things)
