I don't get rage... it is strange? I rather be loosing a good game then winning a bad one too. Winning, loosing, deaths, kills... these don't matter to me anything more then other statistics. All that matters if the fun of the game.
What does get me to quit though is 'behaviour unbecoming a gamer.' This is where you have people going out of their way to do the sort of things administer normally kick for. Simply because... well they are defective in their brains or something? No point in playing against these people ,so I don't bother unless I know an administer is on... then I stick around. All to get that warm glow when they get slapped into orbit every time they walk out of spawn.
I have occasionally 'demoralised quit,' not really rage cause I didn't have any hard feelings for the enemy when this happens. No, these are normally rounds where I am more likely to shoot my own team members for doing the most stupidest of things imaginable. Goddess, every server always has a handful of morons but when they all stack onto one team and your forced to deal with them... no one should have to do that! The hardest part about this is they do NOT listen, particularly in games that require team-play, because then you hitting your head against that wall twice as hard. First for having to deal with them in the first place and second because you're stupid enough to think you can salvage a game that even a god couldn't save.
L4D is one of the biggest culprits for this.