Treat others as you want to be treated, not if they deserve to be treated the way they've done to you. You are representing who you are, not how to get even. Be the bigger person. Be the mature one. But sometimes things just have to be done, and people need to be reminded sometimes of their own medicine... and if it's from the same person who thought like above in the previous sentence, it will be noticed. It's not about getting even, it's about something bigger.