"Holy Day of Obligation" means that attendance at Mass is mandatory. Of course everyone should be encouraged to treat New Year's Day as sacred, but also we should be free to celebrate the day and its sacred quality in our own ways.

As for "serving God," that sort of language is indeed traditional. But it deserves to be rethought. It's really the inheritance from the Bronze Age anthropology of Mesopotamia, in which humans were said to have been created to be the gods' servants, with no clear conception of their own interests. This becomes a commonplace in the biblical and post-biblical traditions, as can be seen in all those Muslim names beginning with "Abdul-," e.g. the most common, "Abdullah." These all mean "the slave of" God, or else some title of God.

If we want a truly humane, humanistic system of beliefs and practices, we can do better than this "service" talk.