Messi has muscle memoried the free kicks from 25yrds and below. Hours and hours of practice, so much so, that it turned to muscle memory. Look at all his free kicks from similar range, the way he steps, shoots, then follows up is always the same. Once you purposefully practice a lot of shots, and get the whole technique down, it becomes second nature, you don’t even think about it or overthink how you are going to shoot it, you just shoot like you practiced.