Burnout
"If you have ever seen a building that has been burned out, you know it's a devastating sight. Some bricks or concrete may be left; some outline of windows. Indeed, the outer shell may seem almost intact. Only if you venture inside will you be struck by the full force of the desolation."
— Herbert Freudenberger, Burnout: The High Cost of High Achievement (1980)
Freudenberger coined the term. He would know.
You keep showing up. You keep producing. From the outside, everything looks normal. Inside, the rooms are empty. The thing that used to drive you just isn't there anymore.
You don't burn out in a day. You burn out over months of saying yes to things that cost more than they pay. By the time you notice, you're already there.
It's giving too much, for too long, with too little in return.
Burnout and depression aren't the same thing. But they share a wall.
"Dark thoughts will echo off the walls of your skull, they will distort and magnify. When you open your mouth, these thoughts go out."
— Dan Harmon, on Twitter (November 2017)
I don't have a fix for this. I've been through it more than once. The only thing that's worked is noticing it earlier each time. And not keeping it to myself when I do.