Frequently when I've searched on the internet, I've had an eHow "How To" come up in the search results, and occasionally I've found them helpful. I happened to come across this one the other day, and though I was surprised they had a "How To" for this, I thought it wasn't half bad. I chuckled when I saw that the difficulty of this "How To" is "challenging", LOL.
"Everyone gets hurt or disappointed at some point. Some people are able to shake things off and move on. Others hold on to resentment for years. If you are holding a grudge, follow these steps to forgive and let go."