One of the problems with being at the top, of achieving something big, and yes being President is big, is that when it's done, it's done. We're seeing this played out with John Lewis and we'll see it with the Obamas. How do you put meaning back in your life after you've been on top? After you have some big, momentous event, discovery or moment, what next you your life?
This is a life view I've observed with others as well as myself. Not that I was ever "famous" but when you accomplish something in one field of endeavor, rarely do you go on to remain on top or accomplish newer and bigger things. Books, TV, and movies have given us the view that a the same person will rise to the occasion over and over. Superman, Batman, John McLain, John Wayne, & Gibbs, come to the rescue week after week, movie after movie. But in real life you're lucky to get one shot at something big. Most police never fire their guns in the line of duty, much less in multiple encounters. Most scientist have one big discovery. The opportunity to be a hero may, may occur only once in your life.
Celebrities, of course are looking for another movie, another song, another show or some way to keep themselves in the limelight. A few do achieve repeated success, but most just fad away. It's a fleeting pursuit. And it's why some do outrageous things to keep themselves before the public. To be important if only in their own eyes.
As far as President's go, TDR quickly put POTUS behind him to be a hunter & explorer. Carter changed to humanitarian. The Bush's have for the most part been content to carry on with their own lives, interjecting some good but not seeking the limelight. I think Bill Clinton would be content to just retire and do some humanitarian stuff. But Hillary and the Obama's are like the Kardashians. They will make every effort to keep themselves in the limelight. To interject themselves in current events, just for the purpose of their own self worth under the guise that they know better than the rest of us what's good for the country.
An aside of this is to know when to move on. To understand that timing, current events and situations put you in a position to do something great. Heroes are those that rise to the occasion when it demands. But those situations are fleeting. Fame is fleeting. Continuing to advance some field of research is fleeting. Celebrity status is fleeting. As the newspaper industry use to say, they're wrapping fish with yesterday's headlines. Recognize when to hold'm, when to fold'm, when to walk away and when to run.