WHAT KEEPS GHOSTS GOING seems to be usually some ancient tragedy they can't cut loose from or some dramatic event they are perpetually reenacting or some unfinished business they never seem able to resolve. They are so shadowy that it's hard to believe they exist. Some of the more spectacular hauntings—cups and saucers flying through the air, midnight wailings, a haggard face at the window—suggest they may have grave doubts on the subject themselves. It seems to be that if they can only make somebody's hair stand on end, possibly their own even, it helps convince them they aren't just figments of their own imagination. They prefer deserted places because they feel deserted. They disappear at cockcrow because the idea of seeing themselves, or being seen, for what they truly are scares the daylights out of them.
If you want to see one, take a look in the mirror someday when you yourself are feeling particularly haggard and shadowy.