break (one) of (something)
To stop one from doing a habitual action or activity. I was able to break my sister of biting her nails by regularly taking her to get a manicure with me. I need to learn how to break a toddler of tantrums because they are a common occurrence in our house these days.
break someone or something of something
to cause someone or something to stop practicing a habit. We worked hard to break the dog of making a mess on the carpet. I don't think I can break her of the habit. Tom broke himself of biting his nails.