When it becomes a habit

So I think I started picking at the skin on the sides of my thumbnails and at the tops of my thumbnails when I was in the fourth grade. I know they say dermatillomania can be caused by stress, but it stopped being something I do when I'm stressed. Now I do it when I'm bored or anytime really. It's absentminded. I want to stop because it's totally gross and I feel cannibalistic. Does anyone have good ways of how they stopped? Sometimes I sit on my hands, but that gets uncomfortable. -lizzz