[SyneRyder]

Going outside in sunlight and walking to a park is my healthiest trick. But my most effective trick is going to a cafe & ordering a Large Chocolate Mocha with 2 or 3 shots of coffee. (Failing that, a chocolate ice cream sundae usually works too.)

When I was in Berlin, on the rare bad day, I would go to my closest train station, sit on a seat and watch the people go by. Inevitably someone would come up and ask me for directions. Helping someone even with my terrible German skills cheered me up.

These tricks aren't long term fixes (walking & sugary mochas won't help you earn more money), but they might give enough of a short term boost that you can get back to working on something productive, and thinking about how to fix the bigger issues (improving relationships, finding a better job, making new friends etc).