Shane Parrish was a cybersecurity expert at Canada’s top intelligence agency and an occasional blogger when he noticed something curious about his modest readership six years ago: 80 percent of his followers worked on Wall Street.

The blog was meant to be a method of self-improvement, helping Mr. Parrish deal with a job whose pressures had increased with the growing threat of global hacking. But his lonely riffs — on how learning deeply, thinking widely and reading books strategically could improve decision-making skills — had found an eager audience among hedge fund titans and mutual fund executives, many of whom were still licking their wounds after the financial crisis.

“People just found us,” Mr. Parrish said. “We became a thing on Wall Street.”

His website, Farnam Street, urges visitors to “Upgrade Yourself.” In saying as much, Mr. Parrish is promoting strategies of rigorous self-betterment as opposed to classic self-help fare — which appeals to his overachieving audience in elite finance, Silicon Valley and professional sports. His many maxims cite Ralph Waldo Emerson, Bertrand Russell and even Frank Zappa. (“A mind is like a parachute. It doesn’t work if it is not open.”)

Today, Mr. Parrish’s community of striving financiers is clamoring for more of him. That means calling on him to present his thoughts and book ideas to employees and clients; attending his regular reading and think weeks in Hawaii, Paris and the Bahamas; and in some cases hiring him to be their personal decision-making coach.