Sometimes vacation makes it worse because it makes you realize just how much your job makes you unhappy.
I'd like to try and take GP's analogy a bit further:
- thermal paste dries out and becomes brittle due to sustained overheat
- resulting in bad contact between heatsink and CPU
- CPU (returns from vacation and) finds that even small efforts makes core temperature rise quickly, thermal throttles constantly
1. It has physical symptoms.
2. It doesn't go away when you stop.
Vacation is good. But two weeks after my vacation I had a rough couple of days, nothing that I couldn't handle before, and I was right back where I started.
I've come to think of it like a mental equivalent of a torn muscle. Recovery takes time—probably far more time than I expect, and if you overexert it, even a little, you'll do a lot more damage a lot faster than you did the first time around.