From the Treasury of Daily Prayer:

Advent prepared us for the coming of the Savior, the fulfillment of the promise first made in the Garden of Eden in response to the sin of Adam and Eve. Christmas is the day we celebrate that hope fulfilled. Jesus is the only hope of the world, because Jesus is the only one who could set us free from our sins. The commemoration of the Nativity of Our Lord puts before us once again the story of the long-awaited King who left His heavenly throne to enter time and become human like one of us. When God wanted to save you from your sins, He did not send a prophet or even an angel. He sent His own Son into human flesh just like ours.