This quote is by Robert Fulghum in his book It Was on Fire When I Lay Down on It. It is found in a chapter which discusses how we have come to associate ourselves, who we are, with what we do. When people on a plane or elsewhere ask Fulghum what he does, he used to make up answers because he did not think what a person is could be captured by a title on a business card or a quick word to describe a his job.
The quote you mention is found in the last lines of the chapter, after Fulghum proudly announces he has finally thought of just the right thing to put on his business card. His card only has one word on it: "Fulghum." His job, he says, to be himself in the best way he knows how:
What I do is to be the most Fulghum I can be. Which means being a son, father, husband, friend, singer, dancer, eater, breather, sleeper, janitor, dishwasher, bather, swimmer, runner, walker, artist, writer, painter, teacher, preacher, citizen, poet, counselor, neighbor, dreamer, wisher, laugher, traveler, pilgrim, and on and on and on.
I and you – we are infinite, rich, large, contradictory, living, breathing miracles – free human beings, children of God and the everlasting universe. That’s what we do.
You are undoubtedly supposed to give your own response to this quote, and you may respond to it differently than I. For me, this quote is a reminder that, though I may have many things in life I have to do and many things which I am able to do, my primary "job" is to be myself. There is no one else like me in the universe, and being me is a full-time, miraculous, and worthwhile job because I am a child of God and a citizen of this planet. And that is enough for me to conquer every day.