Habit, if not resisted, soon becomes necessity.

The saying distills a theme strongly associated with Augustine’s moral psychology: repeated actions form habits that, over time, feel less like choices and more like compulsions. Read this way, the line warns that small, unopposed patterns—especially vices—can harden into a kind of inner bondage, narrowing freedom and making change increasingly difficult. It also implies a practical ethic: resistance is easiest early, before repetition entrenches desire and expectation. Although often cited in religious contexts (sin, temptation, conversion), the insight generalizes to any behavior: what begins as voluntary can become “necessary” through the force of habituation.