Our man on the ledge posts a Blaise Pascal quote on how the past and future mess with our present. Jeff also pointed to Project Gutenberg's e-publication of Pascal's Pensees, where I happily spent a half hour of my present pondering the differences between the 17th and 21st centuries. I stopped reading when I came to this:
"In writing down my thought, it sometimes escapes me; but this makes me remember my weakness, that I constantly forget. This is as instructive to me as my forgotten thought; for I strive only to know my nothingness."