"You are me and I am you"

I ran into the post office to mail a package today.  As I stood in line, I noticed a man at the counter who seemed to be having a difficult time.  He kept repeating the same thing over and over to the postal worker.  This went on for about 5 minutes.  Finally, another man came in to help us.  I commented on the patience of his colleague, how gentle and kind he had been.  My frustration melted as he spoke of the customer who comes in often.  It made me think that that could have been me.  I wanted to slap myself for being annoyed at all.  Make a ripple, give up judgement, see what happens.