Art by smbc-comics
Consciousness is often said to disappear in deep, dreamless sleep. We argue that this assumption is oversimplified. Unless dreamless sleep is defined as unconscious from the outset there are good empirical and theoretical reasons for saying that a range of different types of sleep experience, some of which are distinct from dreaming, can occur in all stages of sleep.
Pubmed Articles
Does Consciousness Disappear in Dreamless Sleep?
Sciencealert Article We Were Wrong About Consciousness Disappearing in Dreamless Sleep, Say Scientists
It's terrifying at first, but if you reflect over it further it becomes natural. Sure, we can't guarantee that we are the same continuous individual, but "not sleeping" would only see us have a more profound and permanent discontinuity. It's not a possibility for us. Still, we do carry something of the people we used to be regardless. Consciousness vanishes and recreates itself, as do most of our cells. We are evolving entities, as is everyone around us.
This existential fear is rooted on a desire for permanence that we never had to begin with. There was never a fixed self that we could possibly know.