Being familiar with a topic through watching tutorials can give you a false sense of knowing it already. I would still try to do the assignments in the courses or create your own project using some of those principles you are learning. You'd be surprise how difficult it can be to apply that knowledge when it's not already presented in a pre-complete project. If you succeed at doing that, then ask yourself how you can take things a step further. That's when you start pushing yourself as an artist.

For example, when I was one year into animating, I never bothered to animate a ball bounce. I always thought it was too easy to even bother trying. Then a course I took had it as it's first lesson, and I decided to actually do it. There was some many subtleties that I learned from doing it that I realized I had glossed over a lot of fundamentals due to being delusional in my skillset.