Most helpful to me was Julia Cameron's The Artist's Way with its exercises. But I didn't find my way until I was about 50 or so, and was surprised that it wasn't something new or different that I'd been doing all along, but was going back to something in my past and combining it with a newer interest, etc. Things change as we're living through them and that's hard to see; we're constantly getting better at some things, enjoying some things and letting others slide, etc. and it doesn't become clearer until maybe decades later.

I imagined being 85 and near the end of my life and thinking back upon it and wondering what I would "regret" not having done? That's a good exercise.