The evil implanted in man by nature spreads so imperceptibly, when the habit of wrong-doing is unchecked, that he himself can set no limit to his shamelessness.

Cicero

Habit is the nursery of errors.

Victor Hugo

No habit or quality is more easily acquired than hypocrisy, nor any thing sooner learned than to deny the sentiments of our hearts and the principle we act from: but the seeds of every passion are innate to us, and nobody comes into the world without them.

Bernard Mandeville