Learn something new.
The thrill of starting as a complete noob that fumbles through the basics to a competent amateur is amazing.
Having a huge well of diverse experiences speeds up the process. Being an athlete makes learning a new sport easier. Being bi-lingual makes learning a third language easier. Building your second, third, or fourth company is exponentially easier than the first.
Get out there. Be a noob. Fumble your way through it. Learn lessons. Move on.
Your mind (and body) will surprise you at what it can do.