Always remember that your physical and mental health is worth more than your job.
You are not obliged to make yourself unwell for a job. It doesn't matter how much you love your job, or your coworkers, or your customers/clients/patients, or your boss. You have got to love yourself more. You must prioritise your wellbeing.
You are not morally or ethically obliged to work yourself to exhaustion or breakdown for anyone or anything other than yourself. Yes, even if you're a frontline health worker. Yes, even if you're a first responder. Yes, even if other people's health or lives might depend on it.
Your body and mind need rest and one way or another, sooner or later, it will stop asking and nagging, and start demanding and breaking down. If you work yourself beyond breaking point, and become permanently disabled, you might never be able to work again.
I know healthcare workers are underpaid, understaffed, and underappreciated. I know when your work is saving lives and physically caring for people, you are particularly prone to guilt when resting, and work extra hard and extra long hours because of it. How many lives can you save if you're permanently disabled because of your exhaustion? If someone dies because you're so exhausted you can't function, that is not your fault; that's the fault of the management who wouldn't get you the help you needed.
I know that a lot of jobs expect you to work "reasonable" overtime without ever defining what that is, exactly. "Reasonable" overtime shouldn't interfere with the rest of your life. If you're missing meals, appointments, or sleep, it's not reasonable. If you're so tired that driving home feels dangerous or you're falling asleep on public transport, it's not reasonable. If it is impacting your wellbeing in any way, it's not reasonable. Never, ever, no matter how important you think it is, do unpaid overtime. If you are working, you deserve compensation. If they expect unpaid overtime to make their profit margins work, that's a problem with their business model.
If your job doesn't have enough staff, and you work extra hard to close the gap, stop. Don't close the gap. If you close the gap, even if you're complaining about it to management the whole time, management will consider the gap closed, and won't do anything about it.
This all goes double if you work for a profitable corporation. If they're profitable because they're understaffed, that's a problem with their business model. If they're understaffed because they won't offer high enough wages, that's a problem with their business model. If you can't complete your duties in the allotted time, and you've told management that it's not possible, and they haven't done anything about it? That's not your problem, it's theirs.
If you don't let it be a problem for management, they'll never act.
This rant brought to you by a former retail & office worker who overworked herself to the point of permanent disability, and with friends in healthcare who have done the same.