I have CFS, and the brain fog really is absolutely awful.
Just around 5 years ago, I was at the top of my game, and could accomplish in one day at work what would take a team of colleagues a week to do.
Now... gods, everything just seems to take me forever! I'll think "that'll take me an hour", and I'm still working on it days later. I keep catching myself staring at the screen like I'm in a trance, and yak shaving to avoid more complex tasks. I frequently forget what I was even doing.
It's hard to describe, but it's like my thought process has slowed to a crawl - my "inner monologue" remains normal, but everything else is just slow as hell. It's really difficult to focus on tasks. 5 years on, and I still overestimate my abilities; it just feels so alien still.
It's pretty much ruined my life, so yeah, don't underestimate brain fog.
That being said, we're lucky that we still can do the things we used to, albeit slower. It's only when you absolutely cannot do certain things that is really daunting.
You are right how people cannot imagine the impact it has on oneself. Headaches, inability to focus, head pressure, anxiety, among other things. The struggle is real, including the fear of getting a full blown stroke at any moment.
Stuff like this is not helpful. Unless you've personally had brain trauma, you probably don't understand what it's like to live with constant brain fog, and to spend extra time understanding abstract concepts that used to be easy. It adds up and wastes your free time. There are no positives about it.
> I know worrying can be a vicious cycle. Trying to improve is the best you can do to grab yourself out of it.
On the other hand, this is helpful. Because worrying about something you can't change can only make it worse. What helped me personally is adjusting my expectations (and expectations of others) and just living my life day to day, trying to enjoy it as much as possible.