This is probably the very last thing I'd want to do in a competition, like a quiz bee. It distracts your mind from the most important thing: the correct answer. It is okay to check, but to doubt your guts is another story. Add the time limit, and surely you will lose a point or two or three.
This is what I did while in the elimination phase of my school's science quiz bee. I doubted my guts. I was at first "hey option A seems to be the correct answer" but then after that it became "wait but B is not yet being a correct one, and there were already a lot of correct As before, we should go for B". So I went for B, and guess what? The correct answer is A. My frustration is immeasurable.
So moral of the story? Trust yourself. Trust your guts. Especially if there's a very small time limit to write your answer. Quiz bees, contests, or any competition don't just look for the smartest. They look for the best diskarte.