Our minds must relax: they will rise better and keener after 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. Unremitting effort leads to a kind of mental dullness and lethargy.
Seneca the YoungerSome there are that torment themselves afresh with the memory of what is past; others, again, afflict themselves with the apprehension of evils to come; and very ridiculously both - for the one does not now concern us, and the other not yet ... One should count each day as a separate life.
Seneca the Younger