Stress and burnout are different things

Stress is too much. Burnout is empty. Treating one as the other is why people take a week off and come back no better.

Stress is the pressure of demand exceeding capacity right now. It is uncomfortable, it is sometimes useful, and it goes when the demand ends. You feel wound up, urgent, unable to stop thinking about work.

Burnout is what stress becomes when it does not end. It has three parts and all three have to be there. Exhaustion that sleep does not fix. Cynicism, where you start resenting the work and the people. And a sense of ineffectiveness, where nothing you do seems to matter.

Burnout does not feel like stress. It feels flat. Stress is fire and burnout is ash. Somebody in burnout is often not visibly struggling; they are quietly doing less, caring less and going through the motions, and this is why managers miss it.

A rest does not fix burnout. A week off helps stress and returns you to the same conditions that produced burnout, which is why people come back and collapse within a fortnight. Burnout requires something to change: the workload, the control you have, the recognition, or the fit.

Where it comes from, and it is usually not the hours. It is having no control over how you work, no recognition, unclear or contradictory expectations, unfairness, or doing work that conflicts with what you believe. Long hours on work you control and believe in exhaust people far less than short hours on work they cannot influence.