The mind should not be kept continuously at the same pitch of concentration, but given amusing diversions. Socrates did not blush to play with small children; Cato soothed his mind with wine when it was tired from the cares of state; […] Our minds must relax: they will rise better and keener after the rest. Just as you must not force fertile farmland, as uninterrupted productivity will soon exhaust it, so constant effort will sap our mental vigour, while a short period of rest and relaxation will restore our powers.

Seneca — On Shortness of Life