First two guys got it right. Try to control yourself and don't shoot at animals that are on alert. The other thing is to get that bow as quiet as a mouse.

Deer don't JUMP the string. Usually they are alerted by the noise of the bow. In the short time it takes for them to hear and react they can drop nearly their vertical body size, but they aren't JUMPING the string or ducking the arrow but their natural reaction is to load up their muscles which causes them to crouch lower. It all happens in less than a half second.

Believe me. There isn't a bow made that shoots fast enough to counter the reaction time of a deer reacting such.