Some people find it exceedingly hard to forgive others. That can just cause YOU so many problems. It will make you sick, literally. It will stifle your spiritual growth, and it just takes so much ENERGY to stay mad!
I don't know why I am the way I am. God had something to do with it, for sure! I just don't stay mad at people. I don't hold grudges. I forgive, but alas, forgetting is harder. Yes, it IS! It is almost impossible to actually forget, meaning you can't recall the incident at all, ever again. But forgetting is more like not holding it against the person, not letting it control your actions towards that person, realizing that GOD FORGIVES YOU AND FORGETS you hurt him! Wow, that's an incentive!
I've learned forgiveness from watching the Master, as I know God has truly forgiven me for some of the hideous, unexcusable, sinful things I have done in my life. If I didn't know that in my soul, I really wouldn't be able to function!
I found an interesting website with some good food for thought if you are having trouble forgiving and/or forgetting.
If you think forgiving is a sign of weakness, a sign that that says "go ahead and hurt me", then think again. It's a sign of strength, a sign that you care more about the person than the hurt, or the potential to be hurt again. And don't forget Psalm 130, my friend...
