I've been struggling with this a lot since I was a kid and it's not even a nervous habit anymore--it's just something that I do. Luckily, I'm a little more conscious of it than some, and I never bite too low or close to the skin. That said, it's still a bad habit and one that I can't seem to stop. 

So, does anyone have any advice on how to go about stop biting my nails?