Watching the stock market over the past year and a half has been like riding one of those rickety wooden roller coasters: sometimes it's exhilarating, sometimes it's terrifying, and by the time it's over for the day you feel beaten to a pulp. The Dow plummets by hundreds of points and it's the end of the world as we know it. It jumps by a similar margin, like it did yesterday, and Jim Cramer actually ascends to heaven on a winged steed. All this proves is that, when it comes to investing, people are anything but rational.