This habit is most common between the ages of ten and eighteen, and roughly 10 to 15 percent of adults over the age of thirty still bite their nails. Since the majority of people are able to outgrow the habit, why are some unable to kick nail biting to the curb? Like any other stress-related behavior, some are better at controlling it than others. It could be that most people learn to deal with stress in new, less obvious ways or develop other ways to cope with boredom or nervousness. With age comes an awareness of social norms and proper public behavior, so we adopt less public (and therefore more socially acceptable) coping strategies. Plus, some resort to nail biting more frequently than others, so it makes sense that they could abandon it more easily.