This year I realized that any designer can go on without design courses. If you need to master a skill, it is not necessarily to attend expensive courses. Sometimes we want to know a little thing or we need to learn just a tiny part of the program. And the rest of the information is useless for us at the moment. We just get it and forget it because we do not practice it.
In one word, learn something practically useful to you. For example, if you like kawai design, especially 3D, learn everything you need to make such 3D illustrations. But if your course teacher makes you model something you are not interested in, you’re wasting your time and money. That's why I came to the conclusion that courses are optional and mentoring sometimes is much more useful.