Do not say/do something, if later on I can't do it as well.
Examples:
1] If you are a jerk to me, I should be allowed to be one back.
2] If you are a hypocrite, I should be allowed my moment too.
3] If you talk s**t about my friends, and don't like it when I talk s**t about yours, keep your mouth shut.
4] If you bash who I am dating, I will bash your girlfriend/boyfriend right back.