Aging.

As the long, hopefully-slow march to the big 4-0 continues, I'm reminded as I get older that while I don't get smarter or wiser, I do get more empathetic.  There's almost nothing that occurs in front of my eyes on any given day at which I can't think "well, I've been there."  There's almost nothing that can phase me anymore, or make me judge anyone else.  There's a reason The Grapes of Wrath means more at 39 than 17.