The researchers speculated that the brain capacity dedicated to doing mathematics diverts mental energy from the concentration and focus needed to continue activating motor neurons that were being inhibited by fatigue. Perhaps this explains common stereotypes about math fanatics and the muscular. When you feel tired and mentally fatigued, do something else for a while. It's important to exercise and get enough sleep, eat healthy, and do fun activities.
That's partly why the 40-hour workweek is good. Once you start working too hard, you lose all those other important things that help you function normally. Even so, he says, people who have a lot of math anxiety often do poorly in math, from SAT scores to lab work. And they tend to avoid careers related to mathematics.