Eye as low as you can get it, like shooting a rifle. And line your eye up so that you are looking down the stick to the cueball. Relax your breathing while you prepare to shoot. The U.S. Army trains soldiers to relax and exhale as they pull the trigger of their weapon. I advise the same.
Thoughts can make or break a shot.
Aye there's the rub. Consistancy will bring confidence to your game. If a negative thought enters your mind, step back, take time and get a new look at the situation, and then re-address the cueball. Never allow yourself to shoot a shot if you doubt that the ball will fall. The stroke is the shot.