I have to admit: I get too ambitious in my games more times than I would like. And sometimes, that can lead to disaster.
Take the following game. I grabbed at a pawn in the opening, knowing that I would have to weaken my kingside. My opponent then launched an attack that should have succeeded, but I hung on and prevailed through sheer luck.
So take a risk once in a while, but in a serious tournament game, it's probably not an extremely good idea, especially if you're not sure of the results.