The word sacrifice in the course - like everything else - is not at all what we think it to be.
For us, sacrifice seems to be things we give up: e.g. not eating meat during Lent. Or the ultimate - sacrificing our body for another person.
But none of that is what the course means by sacrifice. Sacrifice in the course is our choosing not to experience the right mind of the Holy Spirit. And the joy and peace and bliss that come from choosing the right mind of spirit.
Seen from that perspective, EVERYTHING in the world is a sacrifice. Including when we are not sacrificing at all - by the world’s definition. Because EVERYTHING in the world - at least when we get caught up in the drama - means we’ve chosen the ego. Which means we are NOT choosing the right mind of spirit. Which means, we are sacrificing our peace.
And Christmas in the course is a synonym for Jesus or the Holy Spirit. He doesn’t mean that literally. But since the world associated Christmas with the birth of Jesus, the course uses that association to suggest that we use Christmas as a reminder that we are a mind - and that all our experiences come from a choice in the mind. And if we use Christmas to return to our mind and choose against the ego (which means choosing FOR the right mind of spirit), then that is the end of sacrifice.