Where I'm from "Thank God" is something you say every day. While nowadays most people say it in an automatic, mindless way, I think it came to be tradition because of a profound sense of appreciation for life by our ancestors. People found themselves in a world where things are not too bad and often pretty good. They looked around them, and while they didn't know why or how they got here, they felt thankful for the life they're given. So they felt and expressed gratitude, multiple times day, each day.
I think that we... all of us, all of humanity... are going somewhere, somewhere beautiful. So be thankful; be thankful for every moment you're alive. And if you're also one of the lucky ones, you have a responsibility to make the world a little better for everyone else.