In an age when everything is branded and angst is pervasive, there can be a lucrative market for commonsense. In hitting on the idea of the “small stuff”, Richard Carlson not only sold more than eight million copies of Don’t Sweat the Small Stuff . . . and It’s All Small Stuff (1997) but turned more than a dozen variants on it, which were translated into a score of languages and sold more than 25 million copies in more than 100 countries.

He suffered a cardiac arrest on a flight from San Francisco to New York as part of a tour to promote his latest book, whose subject was how to quell holiday stress: Don’t Get Scrooged: How to Thrive in a World Full of Obnoxious, Incompetent, Arrogant and Downright Mean-Spirited People.

Richard Carlson was born in 1961, grew up in San Francisco, studied at Pepperdine University, Malibu, and took a doctorate in psychology at Sierra College, Rocklin, California, before setting up in practice.

He collaborated with Benjamin Shield on Handbook for the Soul and with Joseph Bailey on Slowing Down to the Speed of Life, before writing You Can Feel Good Again (1993).

He could have been merely one of hundreds of self-help authors. But one day in 1994 he was stuck in traffic on the San Francisco Bay Bridge, when his three-year-old daughter Kenna asked: “Why is everybody so angry?” He said: “I’m not really sure.”

The traffic was moving; drivers had radios and mobile phones; many were even talking with passengers; some had coffee to occupy them. “It was one of those moments that I realised that many of the things we sweat over really aren’t that big a deal.”

With his wife Kris, whom he had married in 1981, he began work on a new book. In the meanwhile, he was vexed that a foreign publisher had passed off an endorsement by Dr Wayne Dyer of an earlier book as praise of You Can Feel Good Again. He wrote to apologise to Dyer, who replied graciously: “There are two rules for living in harmony. 1) Don’t sweat the small stuff and 2) It’s all small stuff. Let the quote stand.”

Carlson had his title. He set out to offer such advice as not letting oneself get het up if a driver cuts in: “Why not instead simply allow the driver to have his accident somewhere else?” If the “small stuff” was much his calling-card, traffic vexations were a theme, as Carlson surveyed the pitfalls of relationships and business in such books as Don’t Sweat the Small Stuff at Work.

Carlson is survived by his wife.

Richard Carlson, author, was born on May 16, 1961. He died of a cardiac arrest on December 13, 2006, aged 45