When was this said The greatest discovery of all time is that a person can change his future by merely changing his attitude?

The quote "The greatest discovery of all time is that a person can change his future by merely changing his attitude" is attributed to Oprah Winfrey. While the exact date of this statement is not specified, it reflects her lifelong philosophy of empowerment and personal growth, which she has shared throughout her career in media and public speaking, particularly since the 1980s.