Ah, the 'did you clean your room yet' of the art world. Body care is a pain in the arse, but it's just as important as mental health and there seems to be a lot of support here for that.
For me, I know I don't sit healthily because I don't have a desk, so I have some super cool memory foam cushions on the sofa to help with that. Still get pins and needles quite a lot though. And I'm sure I'll look like a quaver when I'm 50 from hunching so much.
I walk to and from work every day (up a mega hill), but on my days off I can be stationary for hours on end, so I try to get up every hour or so to make a coffee, talk to my bird and cuddle the cat, and to look out the window into the distance. Stretch your eyes, guys!
I always reserve the right to drop whatever I'm working on to jump in a hot shower. It helps me think and relax. And, you know, stay clean, which helps you feel like less of a failure to your mother.
At night the comic plays out like a film in my head so I have a notebook and pen there to right down any developments I'll forget in the morning. Doesn't help me sleep better but it's better than nothing.
That's all I can really think of for now, but tutorials made for intensive gamers on how to stretch your hands would probably be a good think to look into if you suffer from RSI. Also watch out for tendonitis, that's a serious bastard to get rid of once you have it.