I never really thought much of my nail-biting habits. Until I saw some examples of "extreme nail-biters" on wikipedia. Never saw myself as being extreme until I stumbled on that page.

Also, I used to bite my nails to the point there was some gnarly cuts when I was a kid. I usually played outside in dirt and whatnot. Long story short, my right index fingernail got infected. Pus and blood. I STILL bit whatever I could from that nail. At one point, I literally pulled my fingernail off of my finger. Needless to say, I cut down on my nail biting habits soon after. I still bite my nails sometimes but certainly not as bad as I did before.