Fool's Paradise Meaning
(idiomatic) A state of happiness due to illusion or false hope.
Example: 1959, John Knowles, A Separate Peace, chapter 3,
The Devon School record books contained a mistake, a lie, and nobody knew it but Finny and me. A. Hopkins Parker was living in a fool's paradise, wherever he was. His defeated name remained in bronze on the school record plaque, while Finny deliberately evaded an athletic honor.
2004, Jenny Booth, "Mean employers blamed for pensions gap," TimesOnline (London), 13 Dec,
A report by the Pensions Commission warned that the number who were failing to save enough for their retirement was higher than 12 million, and said that Britain had been living in a "fool's paradise" for 25 years.