I"m dealing with pretty intense cognitive symptoms also, and awful blurred vision and eye fatigue.
Your distress about all this seems totally understandable. Its just really hard and beating yourself up about it isn't helpful. And this isn't demented, or other more famous forms of cognitive. It just feels like the energy required to think, got zapped. So I start to think, or ponder something, but quickly just replace that with a sigh, and this is too much, stop now, whatever it is.
I don't read much, or for long. Too tiring. And the eye thing. Oh brother- my vision is seriously blurred. So it just hurts to see quite often. Driving- I go a few blocks. Outside is- intense.
I seem to cope by reducing my expectations and waiting for that occasional day when- I feel less awful. They happen now and then. I can no longer feed the ego.
Sometimes this is mostly a giant management challenge and attitude adjustment. Staying in the zone, not overdoing, taking breaks and resting often. Not trying to do hard things. Deciding thats Ok. Sure its disappointing, not the dream, not the plan.
I could go full tragic and dismay over my condition. I just really try not to do so often. And sometimes I think this is an energy issue response as well. I just don't have the energy to sob in dismay, or put alot of fuel on the woe.