Just my opinion, but there seems to be a psychological effect to wearing a mask.  It makes you more conscientious of your breathing and it prevents you from incidentally touching your face.  That, and I feel much less need to shave...  
 
      BTW, much reduced line at the grocery store today compared to the last few times I was there.  I stood at the front of the line for a while finishing my coffee before going in — actually I was the line, no one in front or behind.  Once inside I found the shelves mostly stocked (still no peas), but the quantity limits had been lifted.  I guess the panic buying is over.  
Now we wait for HD to restock N-95 masks... oh yeah, 3M is feeling some heat...