(Latin: habere, to acquire, possess)
A disposition to do certain things with ease, or to act the same way in given circumstances; with ease because the disposition proceeds into action without much reflection or deliberation, and at times without consciousness.
Habit is acquired by repeated acts.
It becomes like a second nature; it determines character and personality; and may be good or bad.
It is a very great aid in the performance of virtuous actions and a fatal influence in evil-doing, though there is no evil habit that, with divine grace, cannot be resisted and corrected.
New Catholic Dictionary