Inspired by a discussion on chat. I bet we have a lot of nail-biters.
I, for one, am a nail-biter. I made an effort to stop it once i developed nicks in my two front teeth in Korea (I'm still skeptical that it was the nail-biting that caused it, since I'd been biting them for years before then), by filing them down with a coarse emory board. However I lost it and could only find fine or medium emory boards in stores, so I resumed biting my nails with the teeth on either side of my chipped teeth.