@parus as @jodeej commented, try to exercise a bit. I honestly do find it lifts my spirits. From WebMD, "When you exercise, your body releases chemicals called endorphins. These endorphins interact with the receptors in your brain that reduce your perception of pain. Endorphins also trigger a positive feeling in the body, similar to that of morphine.Feb 21, 2018".
Yesterday I stayed home and was feeling a bit down about a couple of things. I finally did 7 miles on my recumbent bike and really did help.
I am sure that working on a hobby might help too, but I have no hobbies beyond the computer. I don't do much complex cooking these days, it's all fattening, and I have to really watch that.
JK