You are NOT alone. This is burn-out, and you're right about the "cure." But don't be a hamster on anyone else's wheel. Recapture the joy.

And don't ignore the depression. Do get SUNSHINE. While it appears that depression is the cause of, not the result of, low Vitamin D levels, the pandemic isn't going to help either one. Take a long walk; go work in the garden. Read in the sunshine for 15 minutes a day (shirtless, so you absorb those rays and make more Vitamin D).

Try painting. Photography. Grab some clay and squish till you have interesting shapes. If the brain is all "blah" and doesn't want to word today, give it a rest. Don't beat it up for having a day. Give it something else to do for a little while. Circle back again later.

At least you have your lovely wife to help keep you on an even keel.