Quarterback Peyton Manning is a model for every leader because while he's a star, he's also hard-working, ready to take guidance from others and generous in his advice, writes Kevin Eikenberry. Notably, Manning's work ethic hasn't weakened over his long career, Eikenberry notes. "Too many leaders have forgotten how hard they used to work. Yes, you may put in lots of hours, but are you working as hard and with the focus that you could?" Eikenberry writes.