“Habit is necessary; it is the habit of having habits, of turning a trail into a rut, that must be incessantly fought against if one is to remain alive.”

Source: Outlander

Source: The Moral Judgment of the Child (1932), Ch. 1 : The Rules of the Game, § 8 : Conclusions : Motor Rules and the Two Kinds of Respect
Context: The motor rule. In its beginnings the motor rule merges into habit. During the first few months of an infant's life, its manner of taking the breast, of laying its head on the pillow, etc., becomes crystallized into imperative habits. This is why education must begin in the cradle. To accustom the infant to get out of its own difficulties or to calm it by rocking it may be to lay the foundations of a good or of a bad disposition.
But not every habit will give rise to the knowledge of a rule. The habit must first be frustrated, and the ensuing conflict must lead to an active search for the habitual. Above all, the particular succession must be perceived as regular, i. e. there must be judgment or consciousness of regularity (Regelbewusstseiri). The motor rule is therefore the result of a feeling of repetition which arises out of the ritualization of schemas of motor adaptation. <!-- The primitive rules of the game of marbles (throwing the marbles, heaping them, burying them, etc.) which we observed towards the age of 2-3 are nothing else. The behavior in question starts from a desire for a form of exercise which takes account of the particular object that is being handled. The child begins by incorporating the marbles into one or other of the schemas of assimilation already known to him, such as making a nest, hiding under earth, etc. Then he adapts these schemas to the nature of the object by preventing the marbles from rolling away by putting them in a hole, by throwing them, etc.

§ 4
From Lives and Opinions of the Eminent Philosophers by Diogenes Laërtius

Source: The Greatest Salesman in the World

Source: The Imitation of Christ

Variant: Habit is habit, and not to be flung out of the window by any man, but coaxed downstairs one step at a time.

2010s

Source: The King's Buccaneer

Australians in a Nuclear War (1983)
Context: I have derived immense comfort, hope, faith, inspiration from a great American, the Cistercian monk-teacher-activist Thomas Merton. Initially a contemplative religious, Merton's spiritual drive was aimed at halting the dehumanization of man in contemporary society, a sickness he saw as leading to mass violence and ultimately nuclear war. War of any kind is abhorrent. Remember that since the end of World War II, over 40 million people have been killed by conventional weapons. So, if we should succeed in averting nuclear war, we must not let ourselves be sold the alternative of conventional weapons for killing our fellow men. We must cure ourselves of the habit of war.