Some of my favorite movies are the ones that:
A. Show the end of the movie at the beginning
B. Rewind to how the story began
C. By the time you get to the end you've forgotten the ending in the first place or are surprised by the twist
When we get to Advent, we are ushered into the beginning of a story that gives us the end at the start. The angel tells Joseph, "[Your wife] will give birth to a son, and you are to give him the name Jesus, because he will save his people from their sins.”
There it is, the end at the beginning - "[Jesus] will save the people from their sins."
Advent really acts as a constant reminder of two things:
1. The glory, uniqueness, and special event the arrival of Jesus is into the world (ie - virgin birth, angels singing, wise men traveling, etc.), and also
2. Our sin
It's the reason for the arrival - that we are stuck and trapped in our sins, and yet God sent His son for us.
It reminds me of the old Christmas song - "Long lay the world, in sin and error pining, til he appeared and the soul felt it's worth."
The advent (or arrival) of Jesus is much more than a good, cozy, winter story - it's the beginning of the end of the reign of sin in our lives.