The beginner artist assumes they know how to draw everything right.
The pro assumes that they don't and checks to make sure.
Assumptions are those things that are extremely helpful, because we can't check everything to confirm that we understand how it works. But for an artist, assumptions are natural enemies.
Our brains are brilliant at recognizing stuff around us, but we only consciously remember very few characteristics of everything that we see.
That's why whenever someone attempts to draw an eye for the very first time, it doesn't look like a real eye at all.
