There are things that upset us. That's not quite what we're talking about here, though. I'm thinking rather about those images or words or ideas that drop like trapdoors beneath us, throwing us out of our safe, sane world into a place much more dark and less welcoming. Our hearts skip a ratatat drumbeat in our chests, and we fight for breath. Blood retreats from our faces and our fingers, leaving us pale and gasping and shocked. And what we learn about ourselves in those moments, where the trigger has been squeezed, is this: the past is not dead. There are things that wait for us, patiently, in the dark corridors of our lives. We think we have moved on, put them out of mind, left them to desiccate and shrivel and blow away; but we are wrong. They have been waiting there in the darkness, working out, practicing their most vicious blows, their sharp hard thoughtless punches into the gut, killing time until we came back that way.