I saw this article about brain fog in the New York Times. I'm glad to see this is now recognized as A Thing.
The cognitive impairment known as brain fog is fact of life for people with fibromyalgia (among other conditions). I've had recurrent brain fog for decades. When it's at its worse, I can't do anything except watch a movie or show. Can't read, can't drive, can't focus. Most days I can manage with frequent micro-breaks.
With my whole fibro regimen, I've greatly reduced the frequency and severity of these episodes. the story linked above has good advice for coping strategies, and ways to bolster your general health.
I still struggle with it. But I've also accepted it as fact of my life. Everyone has challenges. I'm fortunate to have many privileges and strengths to compensate.