I know what usually starts me bitting my nails is certain types of movies , and people that likes to argue for fun ,heh,heh,heh. Study the times your doing this and what is going on when you start it . Then you maybe can avoid biting your nails . Another thing is to keep hands doing something like writing in pettalk (but don't get on controversial subjects heh,heh,heh,). Take up crafts ,or gardening . oh yes ! and get a dog like tiny . LOL!