… you must defend your solitude with a fierceness that makes no distinctions whatever. If you have duties, satisfy their demands at the normal time; if you have friends, arrange suitable meetings; if unwanted visitors come to disturb you, graciously shut the door on them.

It is important, during the hours sacred to work, not only that you should not be disturbed, but that you should know you will not be disturbed; let perfect security on that score protect you, so that you can apply yourself intensely and fruitfully. You cannot take too many precautions about this. Keep a Cerberus at your door. Every demand on you from outside is a loss of inner power and may cost your mind some precious discovery: “when the half-gods go, the gods arrive.”

Sertillanges, The Intellectual Life 98