I know what you mean about biting. I don't bite my nails, though, I bite the insides of my mouth and my lips. I do this constantly. I don't know why I do it, but apparently I really like it being that I do it so much.
I used to be a nail biter, but I don't remember how I stopped. I think I just tried to keep them polished.
Don't know if it is anxiety or not, but my husband would say it is self harm.
Tracy