I have biten my nails most of my life. Over the last 5 years or so I've stopped biting them on and off a few times. I have to admit, it really came down to me wanting to kick the 'habit'. I paid attention to what I was doing and would force myself to keep my hands away from my mouth. I had to busy myself with other things. And I found that having nail files all over the house helped alot. I'd work on making my nails look nice. Pushing the cuticles back, smoothing the edges with a file instead of fixing them with my teeth. Putting clear polish on them. And after I actually had little nails I wanted to keep them. I would focus on keeping them looking nice. It took awhile but eventually I broke the 'habit'.

I have gone back to biting them a few different times. The last time it happened I ended up getting fake nails because I hated the way my hands looked after I bit all my nails down to nothing. I couldn't chew on the fake nails. That helped me to break the habit again. It's been well over a year since I've biten my nails down to nothing.