Prior to becoming an author, Holiday served as the former director of marketing and eventually an advisor for American Apparel.

[1] He consulted for author Tucker Max[4] and, later, he worked with Robert Greene[5] on his 2009 New York Times bestselling book, The 50th Law.

[citation needed] The book has sold more than 230,000 copies and was popular with both 2014 Super Bowl teams, the New England Patriots and the Seattle Seahawks.

[16] During a press conference at the Masters in 2019, four-time major champion golfer Rory McIlroy said he read The Obstacle Is the Way and Ego Is the Enemy, leading up to the tournament.

It was reviewed by William D. Cohan of The New York Times, who noted, "But incessant name-dropping aside — which tends to detract from his gripping narrative — Holiday has written one helluva page-turner.

"[21] As of 2018, there were plans to adapt Conspiracy into a feature film with Charles Randolph writing the script and Francis Lawrence attached as the director.

[23][24] Stillness Is the Key promotes a balanced approach to life, of limiting the amount of "noise" and while mostly referencing stoicism, he also makes references to Buddhism, Confucianism, Taoism as well as the Abrahamic religions.

[25] The book is a collection of biographies for more than two dozen philosophers who lived according to the stoic virtues of courage, temperance and wisdom.

[citation needed] Holiday, through his books, articles and lectures, has been credited by The New York Times with the increasing popularity of Stoicism.

[32] In September 2020, Holiday contributed $10,000 toward the removal of two Confederate monuments from the Bastrop County Courthouse to an alternative site.