My brother had a severe case and even sucked on his thumb at night well into his teens. I ended up a nail biter. I bite the nails on my left hand only. The nails on my right hand are used for playing guitar. (I’m weird.) I have stopped several times in my life but return now and again as well. No significant reason I am aware of. I generally bite them when I am very tired. This is also when I am prone to over eating. Perhaps its connected. Hmmm?