One of the big reasons why someone might continue to bite their nails well into adulthood is because it's become a mindless habit. If you've been a nail biter for 20-plus years, you probably don't even think about it when you bring your fingers to your mouth. Reminders can go a long way to help you here. Some recommend putting colored tape or band-aids around a couple of your fingers to alert you. Others bring a little pain into the equation with the old standby reminder: snapping a rubber band against your wrist when you feel the urge. If things are really bad and none of these reminders work, wearing gloves around the house is a more fool-proof, if a bit cumbersome, way to keep your nails intact.