It's easy to get caught up in the rush of production. It's important to step back from time to time and remind yourself why exactly you are doing this particular shot, or effect, or moment. It was not until I got out of the sound studio and into the Mexican burrito joint that I realized the direction I should have given to get exactly the result I wanted. But I was trying to be a good boy and not waste anybody's time.
I sometimes think that the reasons people put up with directors throwing fits over things not being perfectly the way they want, is because the alternative can be worse: a director who makes his day but doesn't get the amazing moment because "this is as good as I'm gonna get."
There is no excuse for being a jerk for the sake of your ego. But you also get no prize for being a nice guy at the expense of the picture.
So take a deep breathe, and ask yourself if you've really got exactly what you were looking for, and remind yourself why you wanted this particular moment, or shot, or effect, and make sure you're getting exactly what you wanted. And if you're not, pushing a little bit might be called for.