You do not want to cause brain fatigue. It is not like a muscle that strengthens from fatigue. Slowly become active with brain activities. If they cause a setback. Reduce the level the next time.

I have said this many times. We all need to learn to recognize the early signs of fatigue. Trouble focusing. Needing to reread a line of text. Feeling glassy eyed. There are many different ways we can start to overload or fatigue. We each need to figure out what they are in our individual cases.

Often, once you notice an early sign, you can stop that activity and move on to something different. I used to go from the computer to a History channel TV show then to something else. I got lots of exercise going up and down the stairs from one room to the next. (computer upstairs, TV downstairs)