Sydney J. Harris? Sydney Smith? Anonymous?
Dear Quote Investigator: Different types of regret may be experienced when you do something and when you refrain from doing something. A statement on this topic has been attributed to two disparate Sydneys: the English wit Sydney Smith and the U.S. columnist Sydney J. Harris. Would you please determine the correct ascription?
Quote Investigator: The column of Sydney J. Harris appeared in many newspapers. In 1951 he wrote a piece that included the saying. Emphasis added to excerpts by QI:[ref] 1951 January 5, Akron Beacon Journal, Syd Cannot Stand Christmas Neckties by Sydney J. Harris, Quote Page 6, Column 5, Akron, Ohio. (Newspapers_com)[/ref]
PURELY PERSONAL PREJUDICES: Regret for the things we did can be tempered by time; it is regret for the things we did not do that is inconsolable.
QI has found no substantive evidence that Reverend Sydney Smith who died in 1845 employed the quotation.
Below are additional selected citations in chronological order.
In 1999 the saying was printed in “What Now? Words of Wisdom for Life after Graduation” compiled by Jennifer Leigh Selig[ref] 1999 Copyright, What Now?: Words of Wisdom for Life after Graduation by Jennifer Leigh Selig, Topic: Regret, Quote Page 12, Andrews McMeel Publishing, Kansas City, Missouri. (Verified with scans)[/ref] and in 2006 it appeared in “Wisdom for the Soul: Five Millennia of Prescriptions for Spiritual Healing” compiled by Larry Chang.[ref] 2006, Wisdom for the Soul: Five Millennia of Prescriptions for Spiritual Healing, Compiled and Edited by Larry Chang, Topic: Regret, Quote Page 595, Column 2, Gnosophia Publishers, Washington, D.C. (Verified with scans)[/ref] In both cases, Sydney J. Harris received credit.
In 2008 a Usenet message in the newsgroup soc.genealogy.britain attributed the quotation to Sydney Smith:[ref] 2008 September 4, Usenet discussion message, Newsgroup: soc.genealogy.britain, From: Andrew Sellon @sellon.vispa.com, Subject: Re: Marriage Witness Index – great news!, (Google Groups Search; Accessed January 31, 2018) link [/ref]
Regret for the things we did can be tempered by time; it is regret for the things we did not do that is inconsolable. Rev. Sydney Smith 1771-1854, Canon of St. Paul’s.
In 2009 a Professor of Marketing at Concordia University published an article on the “Psychology Today” website. The epigraph was attributed to Sydney Smith:[ref] Website: Psychology Today, Article title: Is Regret Experienced Differently Across Cultures?, Article author: Gad Saad Ph.D., Date on website: August 30, 2009, Website description: Psychologists, academics, psychiatrists and writers contribute their thoughts. (Accessed psychologytoday.com on January 31, 2018) link [/ref]
“Regret for the things we did can be tempered by time; it is regret for the things we did not do that is inconsolable.”
Sydney Smith, British writer and cleric (1771-1845)
In conclusion, Sydney J. Harris should receive credit for this quotation based on the 1951 citation. The linkage to Sydney Smith is spurious. The mistake may have been caused by the matching first name.
(Great thanks to Mary Murphy whose inquiry led QI to formulate this question and perform this exploration.)