What's your "Why"?

How would you describe your purpose in life?

There are so many good reasons to be alive! And I know some folks who--in the face of all the options--have zeroed in on one main purpose that describes what they're here for. For someone like me, narrowing the choices like that sounds impossibly difficult, and also a little compelling. What might it be like to have that kind of clarity?! 

I'd love to hear your thoughts on this! What's the thing that you've named as your "why"? (And if there's more than one, share your list!)