What is it you want to do? For me, it's writing. I like it...love it actually. Writing, for me, is like having that crush that I don't ever have to get over. When I'm writing, my mind is engaged. I can hop into fantasy mode and write about dragons and elves or try for a steampunk angle. Maybe delve into something dark and paranormal but not too scary because I don't want to frighten myself. Such are the perils of having a vivid imagination. Writing is a big challenge for me because I have to care for a rambunctious little one and thus, adhering to the whims of my paying gig can be a bit annoying when I'd rather be clacking at the keys of my laptop zipping through a first draft or toiling over revisions.
Writing is MY worthwhile challenge. There is growth in writing, growth in craft, growth in getting to know others aspiring to make this more than a hobby. It's necessary to pick challenges, just like battles, wisely. Don't want to haul your gauntlet everywhere you go, screaming "Challenge" at the drop of a hat. I tried that briefly...didn't work out well. It became a weighted burden, not something I could rise victoriously to overcome.
What's really great about diving into your challenge is that, in your growth, you become more -ers. Better writer. Better reader. Faster. Stronger.