I bite my nails quite alot.I let them grow but when I get nervous or stressed,I chew on them.I have a couple of friends that bite theirs so much that I don't even think they will grow back.
Oh this is something I just cant stop, my nails are so fine that they just break anyway and then when I stress or get nervous I just pick at them more than anything, it is something I have just given up on trying to stop.