A standard carol that I have always loved is “Adestes Fideles” both in Latin and in English.
Enjoy the carols, and remember to celebrate Christmas for the whole season. Festivities should begin, not end, on the Feast of the Nativity.
Speaking of which, I found this odd article in an odd place: “How to Avoid Christmas Depression: The Eastern Orthodox Nativity Fast May Prevent Post-Holiday Blues” at a site’s “Alternative Religions” corner. It is nice to know that we are alternative. Retro alternative, I suppose.