Brain, don't be stupid: can an analyst be productive 8 hours a day

The analyst's job requires hard work of the mind. Keeping dozens of factors in mind, analysing and finding a solution - all day long. The trouble is that our brain is not evolutionarily adapted to this. Our ancestors never had to deal with so many mental tasks. 

Time management helps us find 10 hours in a day for useful activities instead of 8 hours. But the brain's resources are still sufficient for three or four hours. As a result, part of the day is spent on stupidy, social networking, laziness and procrastination. 

Is it possible to make the brain work all 8 hours long? What are its real limitations? Is it possible to circumvent them? 

I will share my findings from 15 years of studying these questions.