Times and life circumstances have changed. There aren't the same festivities now. He knew he wouldn't be home for Christmas again. It wasn't his choice, or hers. Hopefully, things will be different in the future, but this is what it is for now.
So before he left for his long over the road trip, he brought up the big lighted wreath. He took it outside, hooked it up, and hung it around the stained glass window, just like they always did. He did it for her because he knows she loves the holidays and the lights. It is one of their many connections, even though they are apart. They love each other, no matter where they are.
In the midst of the darkness, the light is there at home, burning because of him, and for him.