This is not my quote but the title of a book by Stuart Sutherland first published in 1992 when he was Professor of Psychology at Sussex University. He was also a journalist writing for many prestigious publications - hence the book is both erudite and readable.
I first came across it in the middle 1990s when I was struggling with a particularly irrational situation. I had always believed that if I explained something properly to someone then they would understand it whether or not they agreed with my point of view. Especially the facts of the situation (not talking about "my truth" here!)
I had become involved with an organisation. There were inconsistencies in some behaviour. At one point a member of staff challenged the reporting structure in what was a very small organisation. I did the business-like thing and found their employment contract in which the member of staff to whom they reported was explicitly laid out. They had signed the contract which had been formally countersigned. I pointed this out and was told "it wasn't mean to be like that". I went through it again and received the same reply. When I asked if they had signed the contract freely, I was told "Yes, but it wasn't meant to be like that".
This was just one of the irrational behaviours I encountered. I had never dealt with a situation like this before and many months followed with many sleepless nights and much self-doubt. This book saved my sanity. The situation was ended with a parting of the ways and a successful restructure.
I see that the book was reissued a decade ago with a foreword by Ben Goldacre, author of Bad Science and Bad Pharma and an afterword by James Ball covering developments in our understanding over the two decades following publication. The book is still available and on kindle as well.
I should have reread it during the Covid lock-downs - or perhaps it would have been too depressing to understand more fully the irrationality of so many of the decisions being made.
A quote from Oliver Sacks on the front cover of the early edition "Stuart Sutherland has surveyed the entire range of human irrationality, its experimental investigation, its root causes and its attempted cures in a book which is terrifying, sometimes comic, very readable and totally enthralling. It makes one wonder how Aristotle could have called man a rational animal."