You never know what will be useful ahead of time. Try new skills and they will connect with the rest of your skills in the future. Take online courses that can help you start a passion project. These are a few I have put together about becoming an entrepreneur(they are all free).
For example, making an outrageous power grab to see just how much resistance you will encounter, and then letting yourself be “negotiated down” to a significant power grab, is a technique as old as the hills. My father calls this the “goat and cow” technique: if you want to convince someone to keep a goat in their office, put a goat and a cow in their office. By the time they’re done arguing you down to just a goat, they’ll be thrilled with their victory.
Running the marathon taught me that fearing failure is worse than never trying. Though I had been a runner for years, this was the goal I put off the longest. There was that fear of having to bow out. That I would discover a limit I couldn’t overcome. It’s hard to describe why this was such a mental block, but being unable to complete it scared me to my core. Instead, I learned that by simply committing to something, even if the outcome is not assured, you can surprise yourself.