Is it your job? Is it your family? Is it something you've achieved? Is it something you've done for yourself or something you've done for others?

I often say the most rewarding thing I've ever done is be a mother to my son.

And it's just an ordinary thing to do. Be a mother. Billions of women have done it. No test, no application process. No license. Just get up every morning and share a space, and a life, and everything you've learned along the way, and hope like hell he listens to some of it.

One of the things I tell him is that greatness isn't a big moment or a single event in one's life. It is the sum of how one decides to spend each moment, a thousand mundane choices. Like, should I eat a salad or french fries for lunch? Should I watch TV or read a book for the next hour?

What keeps us from greatness is not the moment of truth, but recognizing the truth in each small moment, and knowing that moment of reward will eventually come.

My son is especially beautiful when he smiles. I try to make him laugh at least once every day. It's my reward.

What's the most rewarding thing you've ever done?