The exhaustion is not from doing too little. It is from holding too much, quietly, for too long.
Burnout does not announce itself. It arrives as cynicism about work you used to care about, a fuse that keeps shortening, and Sunday evenings that now start at four in the afternoon.
A holiday will not fix it. That is not a failure of the holiday. It is a fairly reliable sign of what this actually is.
What is burnout?
Stress is a response to demand. It rises, it falls, and the body handles it. Burnout is what happens when it stops falling and the system that manages it gives up.
Three things tend to show up together. Exhaustion that sleep does not touch. Distance from work you used to care about. And a quiet, creeping conviction that you are no longer good at any of it.
It is not a character problem, and it does not resolve by trying harder. Which is unfortunate, because trying harder is usually the only tool high performers have left.
When to seek help for burnout
Recognizing the signs and knowing when support can help
When rest stops working. When you are getting sick more often than you used to. When you are functional at work and completely absent at home, or the other way round.
The earlier this gets dealt with, the less it costs you. Waiting until you cannot get out of bed is a common plan and a bad one.