http://sfbatraining.com/

The Strangest Secret was a 1956 spoken word record by Earl Nightingale which sold over one million copies and received the first Gold Record for the spoken word, which helped launch the fields of business motivation and audio publishing. It was later adapted into print and video forms.

Earl Nightingale was an American radio speaker and author, dealing mostly with the subjects of human character development, motivation, and meaningful existence. He was the voice during the early 1950s of Sky King, the hero of a radio adventure series, and was a WGN radio program host from 1950 to 1956.