I don't know if this qualifies as a hobby, but I'm an animal lover - 4 dogs (2 boxers, 1 English bulldog and 1 Yorkie), 5 cats, 1 bird and 2 large, fresh-water fish tanks. I love taking care of the fish tanks, for some reason. I find it very rewarding and relaxing.
Taking care of the animals helps keep me motivated and, of course, they give you that good old unconditional love in return. I have 2 cats, in particular, that seem to know when I don't feel well and they will both lay on my abdomen (at the same time) and their body heat and purring feels great.
I remember seeing a show once on working dogs and one woman had a 'Crohn's dog' that layed on her stomach and she swore by it....she took the dog everywhere and claimed it was better than any drug she'd ever had.