You're in a great position to start experimenting right now. Starting your own projects, jumping in as a part-time cofounder of somebody else's, even taking on

You're in a great position to start experimenting right now. Starting your own projects, jumping in as a part-time cofounder of somebody else's, even taking on a few clients; I'd say do it all. The one thing I wouldn't recommend is jumping in head first with no safety net. The fact that you have a day-job is great; you can take the time to feel out your options and figure out what works best for you. The eventual full-transition will be a no-brainer. When you find that thing that you're supposed to be doing, it will be obvious. The important part is giving yourself enough lead-time to really figure out what that is.