Forgiveness is very liberating.
When you blame others for your troubles, you give them control over your life. Being able to forgive, to let it go, puts you back in control. Of course you don't want to let people take advantage of you. But if someone has already harmed you or slighted you, there's no need to continue making it worse for yourself by fretting and worrying about it. When someone cuts you off on the freeway, it's a bad experience.