As we await the coming of Jesus as a baby in Bethlehem, we also await the final coming of Christ in our world, knowing also that Christ is already here among us. Of course, these sound contradictory. Waiting for Christ, while also proclaiming that Christ is here with us gets us out of a purely "brain" thinking, and into the prayers of our hearts. We do acclaim that Jesus came to earth in the Incarnation, and we do acclaim that Christ has infused all of creation with the Incarnation, and we also await the final coming of Christ in which we will be taken up into the arms of God.
In 1 Thessalonians, St. Paul describes this final coming, this final union with Christ and with God in fantastic and mystical terms, and asks us to encourage one another with these words of hope and Joy!
For the Lord himself, with a cry of command, with the archangel's call and with the sound of God's trumpet, will descend from heaven, and the dead in Christ will rise first. Then we who are alive, who are left, will be caught up in the clouds together with them to meet the Lord in the air; and so we will be with the Lord forever. Therefore encourage one another with these words.
To think of Advent merely as a time of awaiting the child to be born would be to glaze over the richer and deeper sense in which God has already infused the world with the Incarnation, and the even more amazing sense in which God will wrap us up into his embrace at the final coming of Christ. So, the season of expectation in Advent moves us into the sense of awaiting that is always with us. So, we should claim this Advent hope and "encourage each other" with these words!