I bite my nails to the point of shedding blood. It's not fun. I once tried not to bite my nails when I was younger, and I was doing pretty well until I cut my thumb with my other thumbnail when the van pulled into the church parking lot, and I didn't have a band-aid on me. So in spite, I chewed my nails off. Yeah.
I've also gained the habit of pulling my hair. It's gotten bad enough I think I have trichotillomania. I had gained a small bald spot in my senior year, so for half of the year, I wore a ponytail. But even then, I still pull my hair. It's awful, and I hate this habit more-so than chewing my nails. Because of it, I really have to keep my hands busy or I start pulling.