Before you start shooting, you perform a few practice lifts of you arm. One way is to close your eyes, raise your arm and then see where you are aiming. Adjust the position of your back foot if you're off the bulls eye. Key is to keep your wrist locked in position.

Once you raise your arm for real, you don't really need to look at the target, your hand and hence pistol will be in the right spot.

All you need then is to fine-adjust the sight alignment, hence why you focus entirely on the front sight post.

Once you get good you just know how to stand and such, so you'll be mostly bang on right away.

For this reason, if you get glasses for shooting, you'll want them made so your best focus is at the front sight.