Man, don't sweat it. Look at the people who get angry on the internet? They're all fruitloops and nutbars. So are you. So am I. So are we all.
And so what? Anger's a natural emotion. Noone can say you shouldn't be allowed to be angry... but if you analyse it (and within the context of a video game) it's probably going to be more frustration at yourself because you were unable to beat your peers at a games.
Practise more, then go back and PWN HIM!