I tell myself to pick a spot right behind the shoulder. Do mental exercises while you are sitting on stand thinking about how you would execute a shot depending on what direction a deer could come in from. Don't look at the antlers, but concentrate on the sweet spot. Try not thinking about the deer "getting away". It also helps at night in bed to mentally replay encounters or possible future encounters with deer and how you will execute flawlessly. The mind can be trained. As was previously stated time in the woods will help.

Good Luck.