I rested my forehead on a grease spot I'd left on the window earlier. The airlines, I thought, must have custodians who clean the windows, or there'd be an inches-thick layer of goo on them from people like me. That thought was proof positive that I shouldn't be allowed to stay up for more than eighteen hours at a time. I have a bad habit of following every thought to its miserable, pathetic little end when I'm tired. I don't mean to. It's just that my brain and my tongue get unhinged. Though some of my less charitable acquaintances would say this condition didn't require sleep deprivation.