Sometimes we come up for air from the busyness of life and realize the life we had dreamed of, imagined, and worked towards is not the actual life that we have. In other words, sometimes life short of our expectations.
Joseph is in a similar boat. He is engaged to be married, things are moving forward swimmingly, they're both respected people in the community, and then he comes up for air and the picturesque engagement isn't picturesque anymore - Marry is pregnant and it's not his. This news cues a process in which he can divorce her quietly, work to pick up the pieces of a broken engagement, and start over.
However, this is just the moment in which God's kingdom comes bursting onto the scene as an angel notifies Joseph that Mary is pregant via the Holy Spirit.
The Christmas season is often a time in which the things that don't appear quite right in our life come into uncomfortable focus - our marriages, our families, our work, our community, etc. However, Advent reminds us that when things don't look quite right, it's often times an indicator that the Holy Spirit is on the cusp of breaking into our world with good news and with a plan to set things to rights.