The phrase "are habit of" usually refers to a consistent behavior or tendency that someone possesses. Antonyms for this phrase could include phrases such as "not inclined to," "occasionally," or "sporadically." People who are not inclined to something may not have a habit of doing it, while those who only do things occasionally or sporadically cannot be said to have a fixed habit. Other antonyms could include "inconsistent," "erratic," or "unpredictable," all of which imply a lack of consistent habit or behavior. Ultimately, the antonym for "are habit of" will depend on the context in which the phrase is being used.