I do find myself getting that way as well. I do, after a while, turn off the game and play something else, but I don't really get competitive. However, I do get stressed.
I used to play for fun, but nowadays, in CoD4, now that my killstreak is 1.10 (8000 kills, 7300 deaths approximately), I HATE getting a negative KD ratio. It rarely happens anymore, but when it does it annoys the crap out of me.
I also hate it when it seems like ALL the low level newbie players are on my team, and all the hardcore 10th prestige players are on the other team. It's even worse when the other team is comprised of only ONE CLAN. You know you're screwed when that happens (as I heard on another thread, they might as well say "Welcome to Bumrape Boulevard").
Okay I'm ranting now, but back OT, when I do even moderately well in a game, I enjoy it alot, but when I do bad, I hate myself.