In the hustle and bustle of starting a new job—maybe in a new city, probably with a whole new set of colleagues—we lose track of the friends we made in college. That takes a toll on personal relationships. By age 25, men and women start losing friends rapidly. Healthy friendships provide support and fun and can actually help you live longer. And in many ways, friends can help you in your career—and not just through networking or calling in favors.