I agree with Siskyou, it does sound like you may be peeking to watch the arrow. I had this when I first started, but quickly gave up on it when I missed a few.

Here is what I do. If you hunt with a gun, you can't see the bullet, so you don't bother. You continue to watch through the scope. Well, you can do sort of the same thing with a bow. Calm yourself as much as you can before the shot and calmly center on the spot you want to hit. Then when you release, hold the bow still and watch the deer through your sight. Most times, you will be able to get a glimpse of your arrow fletching disapearing into the deers' chest. But you must remember, dont worry about where you hit it when you shoot, worry about that after you climb down from your tree and look at your arrow. Have complete confidence in your shot, the rest will take care of itself.