Civilization advances by extending the number of important operations which we can perform without thinking about them. Operations of thought are like cavalry charges in a battle — they are strictly limited in number, they require fresh horses, and must only be made at decisive moments. – Alfred North Whitehead, An Introduction to Mathematics, 1911
(Hat tip to Sebastian Marshall)
This quote encompasses, IMO, the essence of productivity: 1) automate as much as possible, 2) prioritize remaining and more critical operations of thought, and 3) protect your operations of thought from being misused.