Bosses need to make sure they keep a sense of perspective, says Vanguard founder John Bogle. No matter where your career takes you, it's important to care for your family, to retain your humanity and not to let your success go to your head, Bogle says. "Never forget the important role of luck in your life. Never, never, never, never say, 'I did it all myself.' Nobody does it all themselves," he adds.