I'm in great conflict over this right now. I was diagnosed with an endocrine disorder at 29 after several years of worsening illness. I figured out how to manage it and felt bullet proof through my 30s. Then, right after I turned 40, my whole body started to fall apart and I became increasingly ill with a multitude of symptoms...new ones every few months it seemed. Digestive problems, skin rashes, huge bald patches, vision problems, nervous system problems, heart palpitations, soft tissue/ligament/tendon inflammations, severe migraines, chronic fibromyalgia like pain, muscle weakness, etc etc etc. Quite frightening, to be honest. I did a huge long tiresome post on it in Off Topic a few months ago.
Now it's 6 years and a shitload of tests later, and I still have no real concrete answers. I have two new confirmed autoimmune diseases (meaning three total confirmed chronic diseases/disorders, but none of the three should be causing the vast majority of my symptoms according to doctors). So I'm assuming I have something else lurking undiagnosed. I'm considering going to Mayo, but I've spent so damn much money the past few years I have to save up for the co-pays. My doctors are tired of me, and are starting to just shrug and offer anti-depressants, which would be fine if my main problem was depression, but it's not. The doctors' attitudes come off as dismissive (and sexist, I strongly suspect).
The worst thing was how my ability to do all the things I used to do just dropped away. It felt like pieces of myself were being killed off. Chronic pain made traveling into an ordeal rather than something to enjoy. Sitting at my desk all day to work became problematic and I started falling behind on my workload. Pain and uncertainty wore at my mental state and made me crabby (normally I'm pretty even-keeled). Even gentle exercise was incredibly challenging because I would get 'rebound pain' far beyond normal DOMS. Flares of neurological symptoms made even daily functioning like cutting food for dinner difficult. I gave up field work (which I'd been doing for years). My voice hoarsened and would go out after a few minutes of talking, so even conversation with family and friends has become difficult. I often feel 100 years old, not middle aged.
Bitch bitch bitch.
I'm in a bit of an upswing this summer, symptom-wise, so I'm feeling more optimistic than I have in a couple years...and most notably I'm trying to mull over longer term decisions/plans than I am able to when symptoms are flaring up and I'm just trying to get through each day. During the bad periods, it's hard to even see why I should look forward to a retirement if I'm always going to feel shitty, and potentially keep feeling shittier. Then during better periods, like now, I wonder if I should just STOP WORKING RIGHT NOW.
It's a dilemma. DH makes enough money so that I wouldn't have to work to pay bills, and I am certain that constant desk work is exacerbating some symptoms (mainly pain). Also, if I stopped, maybe I could take better care of myself and also just hit all the remaining specialist doctors that I haven't seen/Mayo, and try to get some answers once and for all, cost be damned.
But it's hard for me to adopt a 'cost be damned' mindset. I have been spending a ton on healthcare for very little gain, and my income covers that, as well as about half our savings rate, AND it helps support both our mothers. So losing my income would definitely be a major hit to our FI plans (currently slotted for ~5-6 years from now).
On the other hand, if things continue to worsen, with or without answers as to why I'm ill...I won't be able to do much to enjoy FIRE in another 5-10 years anyway. And I could potentially run our FIRE bills up hugely, which means I should really keep working as long as possible.
I'm honestly not sure what to do.