A new study out of Virginia Commonwealth University paid attention to what happens immediately AFTERWARDS... and it's not good. Revenge might make you feel good in the moment, but that doesn't last.
The researchers say, "When we follow up with people five minutes, 10 minutes, and 45 minutes later, they actually report feeling WORSE than they did before they sought revenge."
Why? It's because getting your revenge magnifies whatever the person did to you that made you so upset in the first place... and makes you fixate on it even more.
If you just stew about what they did but don't act, eventually you figure out other ways to cope with it.
From The Washington Post - Why getting even may make you feel worse in the long run