Evil habit

Wherefore on no account suffer any evil habit to master thee; but, while it is yet young, pluck the evil root out of thine heart, lest it fasten on and strike root so deep that time and labor be required to uproot it. And the reason that greater sins assault us and get the mastery of our souls is that those which appear to be less, such as wicked thoughts, unseemly words and evil communications, fail to receive proper correction.

St. John Damascene