Talk about suffering. In "A Very Old Man with Enormous Wings," the very old man starts off in bad condition, and it just gets worse. He crash-lands in the storm, gets trapped in a chicken coop, ends up poked and prodded by inquisitive crows, and is then treated like a neglected and unwanted pet. The common denominator? Other people. His sad state, and the lack of compassion by the people around him, is a portrait of the way that the weakest people's suffering just seems to multiply. Just like those pesky exponents in math class.
Suffering is an inevitable part of human (and possibly angelic) life.
Suffering is a result of human interaction. It's in our nature to be cruel and unfeeling toward each other.