The Anchoress has some great thoughts on Ash Wednesday. It is a great moment to remind ourselves that we are mortal and will one day die. As a friend told me at lunch today "You never know, I could check out any minute."
An orthodox Jewish rabbi once told me that to understand Catholicism you have to understand Judaism. The tradition of ashes goes back to ancient Jewish ritual, whereby those in deep mourning would "sit in ashes" as a sign. Job himself, when he lost everything sat in ashes. So the ashes say that we mourn and, of course, they remind us that our body is merely dust.
When I was in law school, we had an ecumenical service where the sermon was given by the University's Anglican chaplain. He noted the gospel that day warns us of public piety, of acting holy to be seen as holy. Jesus in the gospel warns about hypocrisy.
Yet what do we do on Ash Wednesday? We mark ourselves with ash crosses, for all to see. In doing so therefore, are we also not admitting our hypocrisy?
So besides remembering our mortality, we should also use Ash Wednesday to remember our hypocrisy.