When I think of how much I've needed forgiveness in life, its much easier to forgive others. (I didn't say easy, but easier...)
If I held on to everyone's rude or hurtful comments, thoughtless actions or slights, that would basically mean I was telling myself that I've never done that to anyone else. Which of course I have because we are all imperfect, we all sin, and we all make mistakes-whether intentional or not.
A scripture that comes to mind is "even as God freely forgave you, so do you also." For me, that sums it up.
I want to teach my daughter to be a peaceful person. That can be really hard sometimes in this world, but I have to try to show it by my actions. And thats a big motivation for me to be forgiving, the example I'm setting for her.
Btw-this isn't a religious debate. Its everyone's individual feeling and way of coping with forgiveness. (Entropy-the last question that you posed is another conversation all together.)
I have different religious beliefs than many here, but I'm happy to hear everyone else's.