Although it sounds harmless to call nail biting a nervous habit, what's usually going on when you're chowing down on your fingernails is some pretty serious stress. Learning some stress management techniques could go a long way toward allowing you to ignore your nails in times of stress. Breathing exercises are always a healthy way to try to calm yourself. So is meditation. If you don't have the patience for these things, try some good old-fashioned tough physical exercise. Grinding out a spinning class, lifting some weights or going for a long run are all great ways to get the stress out. At the very least, you may be too tired to bother with the nail biting.