This kind of went from a question about sleep physiology to diagnosis of neurocognitive decline, for which I don't have any information to say that you are or are not "fucked", but would be very shocked if you had some sort of irreversible neurodegenerative disorder at age 24.I would continue to give the CPAP time - this is usually the most treatable thing and as you get more accustomed to it the benefit will increase. You had a one-day setback. Depression/anxiety are the other common causes of these symptoms in a young person.
Well I guess I'm fucked judging by how it feels. I don't see how bouncing back is possible to be honest. If I would think about how I felt at the start of this I was certainly sharper than now so there has been a deterioration over the last 2 years. As far as I know intelligence is supposed to be quite intact/stable and if that has experienced a gradual decline then I would guess that full recovery is quite unlikely as well. I say this because if I would think about a topic that I know from experience wouldn't have difficulty thinking about before, my train of thoughts stop earlier than it previously does.