We'll be working hard.
It's normal to have a dirty face when we've been working. Whether we're gardening or cleaning the garage or attic, we often see the smears of dust and dirt on our faces when we go in to wash up. They are outward signs that we've been at work. I suggest that the ashes are equally signs that we're at work. What work? Helping others in need, making peace at work or in our families, visiting or caring for someone who is sick, and yes, even physically working to clean up our planet -- picking up trash, etc.
UPDATE: Do you have a work plan for this Lent? Go ahead, make one. Don't sit on life's couch and watch others do the stuff that heals and helps our world. Your turn. Now. Or else it's just a dirty face without anything to show for it.