I find it helpful to keep a detailed record of all the times I've been wronged, set aside an hour each week to review that record, and then, no less than once a month, explode at the person out of nowhere, and confront them angrily with minute details of all their faults and how the relationship will be forever crippled because of their past actions (or inaction).
Or, you could hold fast to the maxim: forgiveness is a gift your give yourself.
I have also found that voodoo dolls work rather well.
Hairdog (who is, of course, just kidding. But I'll remember that you had so little confidence in me just now to allow yourself to believe, just for a second, that I was honestly contemplating such evil. Yes, I'll remember that. Forever.)
