The tradition of placing ashes on one's head, it is believed, hearkens back to the 8th Century. The earliest description of Ash Wednesday is found in the writings of the Anglo-Saxon abbot, Aelfric - in his The Lives of the Saints, he writes , "We read in the books both in the Old Law and in the New that the men who repented of their sins bestrewed themselves with ashes and clothed their bodies with sackcloth. Now let us do this little at the beginning of our Lent that we strew ashes upon our heads to signify that we ought to repent of our sins during the Lenten fast."
The rite of ashes on Ash Wednesday are recommended to the Christian as an opportunity for repentance and spiritual renewal within the framework of confession and absolution.
That being said, most people think that, for the next 46 days, it is all about "giving something up"... something like candy, coffee, chocolate... something that can be boasted about, something that we can be proud of having "removed" from our lives, without really understanding the purpose of the Lenten promises and Fast.
Why give something up for Lent? My friend and colleague, Rev. Allyson Szabo at Patchwork Interfaith Ministries put it the best...
Why give something up for 46 days? There are lots of reasons. First and foremost, because it's spring, and spring cleaning should always begin with the soul. By giving up some luxury item (or adding some new task to your day, such as daily exercise!), you are taking the time to remind yourself that you are a spiritual being. Second, it reminds us just how privileged we are in our country. We have so very much that often, deciding WHAT to give up can take almost as long as the giving-up. Third, that slight prick you feel when you realize, "Oh, can't have that... it's Lent," that's a wonderful reminder to say thanks to whatever Divine agency you pray to. Thanks for life, thanks for all the things you normally have, thanks for having so much that you can give something up and not suffer unduly.