I recently read the book deep work by Cal Newport. He introduces the concept of deep and shallow work. Deep work is the part the needs focus, concentration and complex thoughts. He argues that there is a limit of about 3-4 hours that one can spend in the state of deep work. That doesn’t mean in can’t do more shallow work in addition to the deep work. But the brain also needs rest, therefore working long hours consistently diminishes the ability to work deep. Also some problems are better solved unconsciously while the brain is resting.

I can really recommend that book, I haven’t adopted to many of the practices that he recommends but I am working on it and it already had a profound impact on the quality of my work but also my general mental health.