The important thing to keep in mind is that you're happy for them, whatever may or may not happen. Sometimes, the only things you can change in life are how you let things affect you.

If you think you can or can't - you're right. This goes to say that, if you think you're going to have something horrible happen on your way home for Christmas, then you're more likely to do things, subliminally, to make it so (like leaving despite knowing there's a big ass snow storm rolling in - I remember that shit). The only thing certain about the future is that it is uncertain. There is a slight, psychological aspect to luck, but I think it has a lot to do with how a person views the world. If you think the world is out to get you, you will make the mistakes that result in bad things happening to you. If you enjoy life and make the most of it, you can't help but have an easier go at it. Being on the defensive and being laid back are two completely different mindsets that translate into more than just an attitude.

Don't worry about it. Your worry would be passed onto them that something bad is going to happen. You don't want them thinking that in the back of their minds.