Applying his superlative new techniques, Cal has his mishaps and his successes, but the filmmakers believe in soul mates forever, and that kind of thing, and the audience may not want to think about the aftermath of the movie, in which Cal and Emily discuss, again and again, that magical year they met in high school.

NEWYORKER: Just the Sex

"I have to believe we're not in a downward spiral forever, " he said.

WSJ: Fans Brace for a Dismal Double Play

In short, investors believe they are flexible and adaptive, but their investments move in a straight line forever.

WSJ: The Experts: What's the Biggest Psychological Trap for Investors?