Since I live in Insomnia land and have since I was 12. A couple times a year my body finally has had enough and I will have a couple weeks where literally I have dozed off in the middle of a sentence or standing.

I have had lots of tests done and seen many doctors through the years no one really had a much of an idea, they just ruled out things that could kill me basically.

What I have determined is that eventually people who don't sleep well just give out and the brain is exhausted from being on full working mode day in and day out that it just basically knock you on my backside and you will sleep whether you want to or not.