When you start that it just proves you spend too much time playing games LOL. I only did it once and that was with a Sega Mega drive game called Cannon Fodder. In it you had a squad of cartoony troops working their way through various battles. A fun game and I tried not to lose a man in as many levels as possible. I got through four or five until it became impossible.
In modern warfare 2, I try to avoid getting hit, after all in real life even a smallish wound knocks you out but the game is designed to make it hard on you. I'm still waiting for a properly realistic game. I thought Operation Flash point was the way forward once it's bugs were refined, but no, it's MW2 that sets the standard and it isn't even slightly realistic.