It's difficult, being aware of your mortality or possessing copious limitations.
Sometimes, being disabled/neurodivergent means complicated medical histories--surgeries, specialists, medication lists longer than a grocery list, susceptibility to illnesses, doctors disbelieving and misdiagnosing. We often have to be careful with ourselves.
For people with chronic pain or illness, pushing themselves can be risky to their health.
People on the Autism Spectrum can become exhausted with too much stimuli.
Those with memory issues may have extra difficulty when they take on too many projects.
It goes on.
But, we all try to push ourselves because we're taught that's how we reach our goals. We push, strive, and sweat until we ache with it, until we shake with exhaustion and tears. If we don't, we don't really want to succeed, we're just lazy and don't deserve it.
Some of us have a more tenuous life span than others. When people feel like they're racing a clock, they tend to push too hard, jeopardizing their health faster (and more often). It creates a catch-22: Race and risk your life or take it easier and don't accomplish what you want/need before you die.
So, what do we do when one day of furiously fast work can set us back days or weeks? We prioritize, figure out the task most important. We start small, with only a five-minute task if needed. We know our limitations and honor them, not pushing to the point of injury or illness. Progress does not have to be made every day, either.
If you're a short story writer, start writing Twitter-fiction or shoot for one short story a month. The writing will add up.
Poets can write haiku or other short forms.
Novelists can start by paragraph... sentence if they must.
Creative nonfiction writers can write in micro-journals.
It doesn't matter where the starting point is as long as the journey happens. It doesn't matter how slow it goes, if it's moving. Some writers take years off between projects and no one thinks less of them, their journeys are just more leisurely. There are benefits in downtime, too. Just keep the path in mind, and visit it whenever you can.
There are no true destinations in the writing life anyway, merely way stations.