I just find it weird that when someone has offended me, I just won't utter a word or even pick a fight with him/her. I just let it pass, and just let karma do it's stuff. And most of the time, it actually works.
Though I admit that I prayed and wished that karma will struck him, most of the time I really don't mean it. Though I get mad, I know it's really bad for someone to wish him bad luck. The karma might bounce back to you.
So what I do is I just say a little prayer for those who have offended me. And pray also that they learn from the mistakes and misdeeds they are doing. I just let the Lord take care of them. I can easily forgive, but will find it so hard to forget.
So if you don't want something bad happening to you, always do good to others.
As the saying goes... Don't do unto others what you don't want others to do unto you.
Always remember that.