Advent is a time of preparation. What are we preparing for? How should we do it?
The USCCB's Advent site reminds us that Advent "...directs our hearts and minds to Christ’s second coming at the end of time and also to the anniversary of the Lord’s birth on Christmas." We are preparing our hearts and minds for Christmas and for Christ's second coming. Advent is a yearly reminder to prepare ourselves, because "the day of the Lord will come like a thief at night". (1 Thess 5:2)
Today's hymn is a good example of that dual-focus - on Christmas (Heaven on Earth) and Eternity (Heaven in ... actual Heaven). The hym is "Creator Alme Siderum", or "Creator of the Stars of Night". (There are other, perhaps more literal, translations of the lyrics, too.) You can look and listen online to one of several versions: one from Milan or this lovely version that shows the Latin on-screen. (Not that any of us need a transcript to understand sung Latin. No sir-ee!)
I suspect a lot of us forget Easter when we're celebrating Christmas. I suppose it feels like looking at a cute piglet and saying "hi, bacon!" (Of course, some of us have twisted senses of humor like that. I've been known to pair a trip to the aquarium with a later seafood dinner.) We have to remember that Jesus is different; Christ is no mere sacrificial animal. He is the perfect sacrifice, and furthermore the perfect priest offering the sacrifice. Jesus didn't come to Earth to teach and then accidentally, along the way, get crucified. God incarnated in Mary "by an act of generous love", as the hymn reminds us.
He "didst from a Virgin's womb proceed and on the Cross a Victim bleed." Christmas leads on to Good Friday and death, then to Easter and resurrection. So while we enjoy Christmas, we have to prepare for Good Friday.
Paul tells us how to prepare. He tells us to "stay alert and sober...putting on the breastplate of faith and love and the helmet that is hope for salvation." (1 Thess 5:6,8) Faith, hope, and love are the three theological virtues, the good habits that are aimed at God and, in practicing them, bring us closer to Him. Read about the theological virtues in the Catechism (paragraphs 1812-1829) and be alert for the opportunities gifted to you today to practice and build them. Find an opportunity to practice each of the three theological virtues today, and take it.