Firstly, I love Advent simply because of the continuity the new liturgical year holds with the old: the Church does a lovely job of switching from talk of the End Times and the eschaton into the time of preparation both for remembering Christ's Incarnation and for His Second coming. It works so well that we remember those who have died with All Saints' and All Souls' Days in November and discuss the End Times in each Sunday's readings. December seems almost a second time to reflect on those words and ponder and work to put them into action in our own lives. To ponder mortality, our poverty of finitude, and reflect on how clearly we are NOT God both in November and as we begin a new liturgical year is fitting during a time of cold, darkness, and possible isolation. The mood that winter sets, that quasi-seasonal affective disorder (or real for those who truly suffer from it), allows us to reflect on the knowledge of our own deaths. They may come soon, they may not, but they truly will come. There is no way to escape it. I find that the thought can almost be paralyzing, but it's a moment of honesty. Death will come. We will be put face to face with Jesus. We will (perhaps the more terrifying aspect of it all) come face to face with ourselves, how we truly are: both what lies in our hearts and what our actions tell of us; both our intentions and how our actions are interpreted by others.
Perhaps this is why I have issue with some songs sung at Mass, e.g. "Send Down the Fire of Your Justice." I guess I just have issue with that line, as it's sung in such a joyful way. There's so much more to Christ's Majesty than everybody celebrating in love and going to heaven. There's the painful realization of what has gone on in our lives, how far we are from perfect, and justice is the last thing I want to be raining down at the moment. To understand a little more how I feel, try googling the image of "national shrine upper church mosaic" to get a look at a jacked, Arian Jesus who's got a blazing look in his eyes that you KNOW will make any feeble excuse wilt and/or melt away. That look would only let the absolute and piercing truth remain, which is beautiful, don't get me wrong, but it's intimidating to say the least. I don't think it's theologically WRONG to sing those lines with that tone. But how many people actually reflect on what the words mean, reflect on the mystery, and then come to sing it with a trust that with justice will also be mercy? To sing that song without having some pause is either to be trite and glib or perfectly trusting in God. It's like what the Beavers say about somebody looking Aslan in the eye without trembling in The Lion, the Witch, and the Wardrobe.
Getting off of that tangent, I love Advent because of the time of year in which it falls (both liturgically and temporally) and I love it because it addresses a fundamental characteristic of being Christian. Christ brought God to the world, but the world persists in evil. We still await the coming of the Lord in glory. We still have to face our own demons. We still have to face our death. Advent is a time to reflect on that, like I said. It's a time to ponder in fear and trembling our frailty and dependence on God. We depend on God because of that frailty, but it's not a grudging dependence on a distant or cold God, nor is it a dependence whose hope disappoints. We hope and wait for God, trusting God, having that final unity with God be a guide to help us as stable footing through an uncertain present. This is why I love the song "My Soul In Stillness Waits." Advent is a time of realizing that we are in process, on a journey, still becoming. It's not always easy or wonderful or lighthearted, but it's fruitful and life-giving and allows us to delve deeper into faith. Of course, once again, the words of that title should give us pause. How still do we let our souls be? As light and cheery as the "Holiday Season" (which soon will start around Easter and envelop Halloween) can make us during a cold/depressing/stressful time of year, how much of it is genuine joy and how much is an attempt to flee from reality? It doesn't mean we should all be killjoys and somber and solemn in this time (see below), but it does mean that examination of where our happiness, hopes, cheer, etc. stems is due.
Thirdly, there's an exhilaration that comes with Advent as we prepare for Christmas. For those a little too focused on the justice of Jesus and are tempted to go legalistic, pharisaic, pelagian, jansenist, etc., we have to remember that climax of the time of waiting: Christ, the Word made Flesh, God's only-begotten Son, entered the world as a helpless babe, was laid in a manger, and was human. The wisdom of years has looked at this self-disclosure of God, this demonstration of self-emptying, and seen from that moment (well, from the conception of Christ, but especially in the birth) the amazing love God has, even for those who would kill the Son of God. That's why I love the song "People Look East": there is a sense of awe and joy that we must have, one of wonderment and rejoicing, that the Word became flesh and dwelled among us. Make yourself ready, don't despair, for love is on the way.
I love Advent because it addresses those realities: where we objectively stand, both as less than dust in comparison to the perfection and majesty of God; our dependence on God for that very reason; and the hope that comes from the demonstration of love made manifest most fully in Jesus. The beauty of Advent, for me, is one that is too abundant, necessary, and life-giving for me to divert most of my energies to singing "Chestnuts Roasting on an Open Fire" (I absolutely abhor that song) or even to Christmas carols, or to bypass it in favor of simply thinking of "pre-Christmas" which culminates in one day of celebration and then ends (whether due to needing to think about New Year's and/or Valentine's Day or just because Christmas is "over"). To do that makes a superficial and trite sham of Christmas: it has its own OCTAVE, it has its own SEASON, partially because of everything that stands at the end of the last liturgical year and partially because of the grace that it is as demonstrated in part through the readings throughout Advent. I love Advent, then, for a fourth reason: it makes Christmas truly meaningful and allows me to more deeply understand and celebrate throughout the Christmas season instead of one day.