They take ashes from Palm sunday from the previous year and burn them and make a sort of ashy pulp. Then on Ash Wednesday (wed before Easter) you have a service and the priest rubs his thumb in the ashes and says "Ashes to ashes, dust to dust. Remember that you are dust, and to dust you shall return." Then he makes a cross in your forehead with his thumb.
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"All my years in p*rn didn't quite prepare me for childbirth. I mistakenly thought all the stretching I did would make this easier."