It's because you aim for a false objective!

There is no a 'proper' way to do it! It goes like this, you change it, if it looks good, well, good job, if not, ask yourself why, and try your best to take that into account next time.

It's by doing millions of small mistakes that you improve. The teacher teaches one way that is kinda easy to grasp, it's not the only way and far from unique.

The further you go, the further you will see the same mistakes, and you will start to think in terms of volumes, shapes, shadows, perspective, even anatomy if you still struggle on some human body parts