From Longman Dictionary of Contemporary Englishbreak a habitbreak a habitSTOP DOING somethingto stop doing something that you do regularly, especially something that you should not do a new drug which helps smokers to break their habit → break
Examples from the Corpus
break a habit• I'd once helped her break a habit.• These three actions are vastly superior to breaking a habit by will-power alone.• It is important to understand that we are breaking a habit, for we have been conditioned to react in this way. 