Stock investing is never smooth. The jagged gyration of the journey is ever-changing. The clashing combination of fresh news, frenzied response and feedback loops is inescapable. For those in doubt, the dramatic plunge and rapid recovery of recent weeks is a jolting reminder. The wise words of the great JP Morgan over a century ago are timeless. When asked what he thought the stock market would do next, Morgan replied: “I believe it will fluctuate.” Paul McCulley was the chief economist of investment management firm PIMCO until his retirement in 2010. Today, McCulley is probably best known for coining the…