The Religion Golden Rule - Islam? I think you need to remind some of your adherents of the rules. We all need to realize that living life in balance and kindness is a work of art, approached with humility, and more precious than any riches.
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.
A lesson that's definitely better to learn late rather than never. I know I'm guilty of making the mistake of assuming things in some of my past relationships; which at times I wished I had handled differently. It would be during my days of solitude, that I would come to realize how the devil manipulates situations and create illusions that are just not so. Although we can never turn back the hands of time for what has already happened, we can always set a reminder for future events.