Honestly, I think this is the crux of the Gospel message. I think this because Jesus calls us to make a decision: "Repent."
The Gospel isn't just a nice story of hope in the midst of suffering. The Gospel involves a personal decision to embrace the cross. That's why the first reading says, "Every spirit that acknowledges Jesus Christ come in the flesh belongs to God."
To truly acknowledge Jesus Christ come in the flesh involves so much more than paying lip service to God incarnate. If God became human in the person of Jesus Christ, then everything that comes after must be true. And if everything that Jesus preached is true, then salvation comes through a personal relationship with Jesus and submission to His will in your life.
That means change. That means prayer. That means radical self-gift.
It's only January 4. There's plenty of time to make a New Year's Resolution to follow Jesus in a more serious way. Let Nativity help you do it. Come to adoration. Go to an additional Mass every week. Join a discipleship quad. Ask someone whose faith you admire to chat and ask them how they do it.