I’m in the same boat. If I don’t get 8-9 hours of sleep, I have to take a nap to function.
I have two sleep disorders that leave me severely deprived of sleep and oxygen almost every night, affecting my brain function significantly.
I’m at my worst when I don’t get enough sleep.
Sleeping less than 8 hours can impair your mental function, even if you’ve grown accustomed to it.