Flow: The Psychology of Optimal Experience

by Mihály Csíkszentmihályi

Activity and reflection should ideally complement and support each other. Action by itself is blind, reflection impotent.

This is certainly applicable to the evolution of the mind: as it has increased its power to handle information, the potential for inner conflict has increased as well. When there are too many demands, options, challenges, we become anxious; when too few, we get bored.