Anticipation. That's what this day is about, whether tomorrow's celebrations are devoted to the birth of a savior or to a frenzy of family love marked by gift-giving carried out on wildly differing scales of delirium.
Christians are quite literal about that sense of joyful expectation. The sacred season leading up to Christmas is even called Advent, which means "coming" or "arrival."
Christmas Eve is the peak of that four-week period of awaiting the child meant to save mankind from its many wickednesses, every last one of which it continues to practice. Christian or not, it's hard to dispute the world needs saving. We seem unable to do it on our own.
Children, of course, have many ways to describe this day. The verbal ones usually include a nonstop stream of excited chattering about the man with the belly who has flying reindeer and a huge sack of neatly wrapped presents that he somehow manages to distribute around the world in just a few hours, effortlessly gliding up and down chimneys -- even in houses that lack them -- all while consuming several billion cookies and a barge of milk, one glass at a time. No wonder the old boy is so big.
Other descriptions exhibit themselves behaviorally. Typical symptoms include compulsive fidgeting, furtive glances up the aforementioned chimney and an earnest but futile effort to stay awake for the visitor's certain arrival (there's that word again). This is not to be confused with adults' efforts to stay awake in a midnight blizzard of ribbon, wrapping paper and bright, shiny batteries.
It's a delicious anticipation, like you get on the last day of work before a vacation trip to some special place. And why not? Christmas is a special place for millions who can visit only once a year and who, however harried the anticipation becomes, are always happy to arrive there once again.