Whatever happens in a roleplaying game, remember that it's only a game. Just because your friends stab you in the back and run off with your treasure and your kingdom doesn't mean you should bear a real life grudge and take revenge on them by scratching their car or whatever. It's just make-believe. It doesn't matter in the real world.

Bottle up your anger. And next time you play a game together, let their character have it. You can't do half the vengeful stuff in reality that you can get away with doing to their character in a game.

Transcript

Anakin: Um... so... what did Ben play in the fantasy game?
Padmé: He was a fighter. He had this side quest thing that he was roleplaying, to make his character more interesting. Like I'm doing now.
R2-D2: {aside} Oh, lord...
Anakin: And Pete?
Padmé: He was a thief. He was kind of in charge of the mission—
R2-D2: {aside} Being the only one with any brains.
Padmé: —but the pirate ninja boss caught up with us and...
R2-D2: Go on. Tell her what you baboons did then!
Padmé: Well, Pete died, but Ben and I saved—
R2-D2: I died because the two people in the party who were supposed to have fighting skills let the ninja get right past them!
R2-D2: Then they left me there.
R2-D2: And later on, when the bad guy was finally dead, they resurrected HIM, so they could JOIN FORCES WITH HIM!!!
Anakin: Sounds like some... er... interesting roleplaying.
R2-D2: Worst. Adventure. Ever.