"Memento homo, quia pulvis es, et in pulverem reverteris." (Remember, O Man, that you are dust, and to dust you shall return).
Today is Ash Wednesday, the beginning of Lent. When I was a child living in still (and way too much) Catholic Québec, a priest used to come to our school and make a cross on our forehead with ashes, saying the words quoted above (although not in Latin). It might seem quite sinister, but I actually enjoyed it. The Catholic rites we performed in school were always enjoyable: they were easy enough to do, they were taking precious school time (when we didn't have to learn anything useful to our intellectual development) and they were more entertaining than "normal" classes. Now I find most of them pathetic operations of propaganda, but the little ritual of Ash Wednesday was at least honest: it was stating a fact about our own mortality. Of course they were trying to spin it into something more positive, talking about Jesus's resurrection and so on, but still, it was more intellectually honest than most of what we were usually doing in religion classes. Therefore I still like this ritual, which reminds ourselves of the certainty of death. Life is more enjoyable when you know it is not permanent.