Even people who went to a university only learned from the work they did. Most of what they learned wasn't on the syllabus. So, treat everything you do as a thing you can learn from. In any textbook you pick up, do all the exercises.

The main thing I learned in engineering school, that I used after, was that not knowing how to do a thing did not mean I could not do it.

If you have to do a thing again, do it better than last time. Maybe the result could be better, or you could get there with less wasted time. Always devote some attention to how you could be better than you are.