If you don't carry a purse, or a man-purse, to keep a file on your person, stash nail files everywhere you frequent. I keep one in the car, work, and home. Being able to quickly file away a snag or imperfection will prevent you from biting your nails.
I find that I most need a nail file when stressed at work, where there's no escape from the snag at hand. Having a nail file easily accessible, in my pencil holder, keeps me ever-ready (and sane!).
So go forth and hide those files like easter eggs!