Currently, I am designing a large game setting with lots going on. There's agricultural production to plan, geography to consider, languages and cultures and weather and religion and warfare and trade -- and narrative plot. I have no one to play FRPGs with, so this may look like so much wasted effort, but it's not. It's just an odd form of self-therapy.
Working on projects like this gives my brain exercise. It makes me feel better emotionally and physically. There's a "flow" to it that is wonderful to get going. Creativity rules, man. As long as I don't obsess over it to the point of neglecting other important things, there's no down side to this. And it's a good sign that I'm coming out of my exhaustion and funk enough to enjoy doing it; for some months, I was too drained even to read a novel.