Burnout tends to build slowly, through months of feeling stretched, before it becomes hard to ignore. Early signs often include trouble switching off in the evenings, irritability over small things and a sense of dread about the working week ahead.
Many people push through these signs for a long time, assuming things will ease once a particular project or busy period is over. Often another busy period follows soon after and the underlying stress never really gets addressed.
Talking to someone outside the situation, whether that is a counsellor, a GP or a trusted colleague, can help make sense of what is driving the exhaustion and what might need to change, rather than waiting for a breaking point.