The reason this matters commercially rather than only personally is that exhausted judgement is expensive. Tired owners take work they should decline, quote badly because the conversation is one more thing, and defer the decisions that compound. The cost of burnout is rarely a dramatic collapse. It is a year of slightly worse decisions.
Separate the two things that produce it, because they need different responses. Working too many hours is a volume problem, addressed by pricing, delegation, or declining work. Working constantly without a clear boundary is a structure problem, and it persists at any volume because the mind never stops running the business. The second is more common in solo businesses and less often recognised.
Take time off before you need it rather than after. Recovery taken while functioning is short and effective. Recovery taken after collapse takes considerably longer and usually costs revenue as well. Booking it in advance, when the calendar is empty, is what makes it survive contact with a busy month.
Watch for the specific signals rather than waiting for a general feeling. Dreading a particular client. Postponing work you used to enjoy. Answering messages at hours you would not have three months ago. Losing interest in the parts of the business that originally motivated you. Those appear well before anything dramatic and they are easier to address at that stage.
And be honest about whether the business is the problem or the arrangement is. A viable business run badly is fixable through process, pricing, and boundaries. A business whose economics require this pace to survive is telling you something structural, and no amount of resilience resolves it.
Protect one thing outside the business and treat it as fixed rather than as what gets cut first. Exercise, a standing commitment, anything with other people in it. Solo business owners lose these gradually and without noticing, and their absence removes both the recovery and the perspective that keeps ordinary problems in proportion.
Watch for the specific trap of measuring your worth by hours worked, which is common in a first year because hours are the only input you fully control. It produces a business where working less feels like failing regardless of the results, and that belief survives long after the business is doing well, which is why some successful owners never recover their time.