Tron.

"Greetings programs!" "Now that is a big door!" "Null unit!" "I play videogames better than anybody!" "Forget it Mr. High & Mighty Master Control!"

What convinced me was my dentist stating that the damage to my teeth will be serious if I continued biting my nails. I just decided one day that I wouldn't bite them any longer. I occasionally get manicures so they look good and that's a confidence boost.