Every year, seeing smudgey crosses on the foreheads of co-workers reminds me what time of year it is and what day it is. This year, I decided to do a little research on the mark of the cross.
My understanding is that priests give the mark while giving a short "ashes-to-ashes" recitation ("Remember Man that you are dust and unto dust you shall return."). So it appears to be a memento mori, a reminder of one's own mortality.
This made me think: The Eastern analogue of this is "the transience of all things" found in Buddhism, Hinduism, and Taoism.
So what's the difference between the two? I think the Western view focuses on the finite and self, while the Eastern view focuses on the infinite and outside the self.
For reasons I don't entirely understand, I think I prefer the Eastern view.