High performers should know Yerkes-Dodson law. It describes the relationship between performance level and pressure.
According to this law, performance level increases only to a certain point and later drops with further arousal. However, there’s an important caveat — it drops for difficult tasks only.
In other words, if you do weight lifting, it makes sense to push yourself. There might be diminishing returns, but (in a rough approximation) the more, the better. However, when you face hard cognitive tasks, the same strategy won’t work. The harder you try beyond a certain point, the larger drop in the output will be.
There are a lot of good reasons to work 4 hours a day