As someone who studied martial arts for 15+ years, the one thing that my sensei would never let go of was the basics. It doesn’t matter if this was your second class, or your one thousandth class, we went over the basics at least once a week. If you are not familiar with the basics, and lose sight of the ground, then you are bound to crash.
This relates to product management in so many different ways. I hear a lot about agile, waterfall, the important of UX, etc. Product managers are constantly trying to learn more, do more. The list can go on for a while, and I really do care about all of these different methods and focuses, but nothing more so than the basics. The most important part of any product is the foundation upon which it was built.