Many shooters peek at the target while they’re shooting. This is a bad habit that can be difficult to break. In this video, AG & AG’s Director of Training, Tatiana Whitlock, explains why:

Sometimes peeking is an exaggerated movement over the sights
and sometimes it is a tiny shift. Either way, peeking adds time to your ability
to quickly recover your sight alignment and get your next shot on target. It
also shifts your mental focus away from your fundamentals of grip, stance,
trigger press, etc. (your emphasis) to the target.

The target is a great way to evaluate what modifications you
need to make to hone in your groupings; however, it’s not an intermittent gauge
while you’re conducting your course of fire.

Finish your course of fire with solid fundamentals, and your
target will be there to review afterwards.

SOURCE ARTICLE: https://www.agirlandagun.org/avoid-peeking/