I know because I've lived it. My other comment on this post:

I have narcolepsy. It took a dozen or so doctors and years of suffering before I got a correct diagnosis, and even then it was only because I diagnosed myself with Google and then specifically made an appointment with a doctor who specializes in it. Gemini nails it when I put in my symptoms.

Also, I had to vouch for your totally legit comment b/c somebody who doesn't want other people to read it flagged it dead.