There are those who rush to the prop closet immediately following practice to grab a towel and the wonderful smelling antiseptic spray in order to de-funkify their mat and wash away any germs harbored by too many Chaturangas.  I used to be that fastidious mat cleaner, but things have changed in the past couple of years.  I’m not saying that I never clean my mat, but there is something about seeing your handprints or footprints and knowing that they are a mark of the time you spend committing to your practice.  Whether you’re rooting yourself in Tadasana (Mountain Pose) or pressing your palms into the mat for Adho Mukha Svanasana (Downward Facing Dog), each imprint on the rubber is a physical sign that you showed up to practice.  Many days that’s a great comfort to me.  So, I’ll douse the mat after a particularly sweaty practice, but otherwise I’ll leave a little dirt for the next day.