I believe there comes that point in life that no matter how things are going and how successful you are you just stop and frankly ask yourself, uh what am I doing? Maybe you know things are getting out of control or it's for some self-assurance that yes, this is in fact what you want to be doing with your career, life, relationship etc. Like climbing a mountain and checking every once in a while that you are where you want to be. And you say hey everything is cool, let's go forward.
Or, if you are like me you have an almost palpable fear of reaching your potential that several gut-checks are in order to make sure you don't FREAK OUT with the amount of things you've taken on/how far you're getting. Like going into a restaurant and ordering the left side of the menu. It's not the waiters fault when they bring it to you.