Some historians believe that it was actually the Romans who started the tradition (like 2000 years ago), siting the practice of decorating trees with small pieces of metal during Saturnalia, their winter festival in honor of Saturnus (the god of agriculture), and that Christmas itself was a political attempt to satisfy the very old and popular pagan winter festival with the new Christian religion.
The point is that today, the northern hemisphere's Winter Solstice, the shortest and darkest day of the year, is one to celebrate.
Today is our seasonal midnight. It's time (if we remember) to says thanks for all things we have, just like we might do before we go to bed.
Today is a reminder that tomorrow and the months ahead – no matter how dark and difficult things are right now – will always bring the promise of brighter and more bountiful days.
Today is the day with the least amount of light, and we should celebrate our ability to find light and warmth in even the darkest and coldest of days ...
But we have to consciously choose to do these things. That's where celebrations and traditions come into play, they help us remember.
The metaphor is beautiful, really.
And I think it's great to keep this perspective while we busy ourselves with the hub-bub of our modern-day traditions at this time of year.