Start by embracing an uncomfortable truth: If you continue on an academic career, work will never ever be done. In the past, it may have been a viable strategy for you to work until you have completed everything you needed to do, and to then have sufficient time to recover before more work materializes. This will no longer work, and it will probably get worse in the future.
There are very different strategies that work for different people. I know colleagues in academia who have strict rules on when is and when isn't work time. By reserving a reasonable amount of time off (and sticking to it), you can obviously prevent work life from expanding to encompass everything.
A more flexible strategy can be to self-monitor for signs that you need a break (whether its 10min, an afternoon, a week, etc), and then to take it. If you are in it for the long haul, sacrificing your physical or mental health just isn't worth it. Whether you take time off on a schedule or when needed, be clear with yourself that you need and deserve time off, and avoid feeling guilt about not working.
Of course, when carving out time off, you also need to make some decisions about how to prioritize tasks for the remaining work time. This is in itself a massively complex topic, but some basic notions are:
a) Plenty of things just need to be good enough. This includes qualification exams and initial documents.
b) Just because someone wants you to do something does not necessarily mean that you need to do it. This holds even more for the "by when"-part.
c) The vast majority of academics is going to be aware of these struggles, and few of us are superhuman. Reach out when needed.
