I would love to know that myself, and in my experience, it's the lack of any concrete proof that you can capture on an MRI, EEG, etc. It basically comes down to a diagnosis of exclusion, which is extremely disheartening. It puts the burden of proof back on an already ill patient, and it almost feels like you have to go overboard in an already weakened state to prove you're as limited for some medical reason, not all in the mind. I know it sounds awful, but I envy some cancer patients or heart patients because they have something definitive. Granted, some of what they go through is way worse than what I have, but it just sucks being invisibly limited. I have really struggled with this in the last few weeks. I hate the dependency this has put on me. I was such an independent person before all this, and now I feel like I have to be at others' mercy and can never have my own say. Understandably, if you are in someone else's car, it's only fair to go by their rules, wants, etc. But it sucks so bad to want to be in my own car, doing my own thing. I didn't want to be a child for the rest of my life, asking someone else for permission or having to tag along.
This. Sucks. So. Badly. It's truly a no-win situation. Darned if you do, darned if you don't.