The marvel of Christmas is that God sent His Son to the earth to be human—to breathe like we do, eat like we do, and cry like we do. God dropped His infant Son into a city too full, a temple too suspicious, and a race (the human one) doomed to sin no matter what. He gave heaven's royalty to be earth's sacrificial lamb, so weary, broken sinners could receive eternal life. That's the marvel of Christmas (although there's really so much more).
The marvel of the rest of the year is that it's always true, not just for the month of December. I personally think we should celebrate the meaning of Christmas all year long.
But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons.