“It's tough to make predictions, especially about the future”
The earliest citations of this proverb, from the mid-twentieth century, refer to it as Danish in origin. See http://quoteinvestigator.com/2013/10/20/no-predict/
Disputed, Misattributed
From Yogi: The Autobiography of a Professional Baseball Player; reproduced in "Berra Dispels Li'l Abner Myth."
Al Abrams, from "Sidelight on Sports: A New One on Yogi" https://news.google.com/newspapers?id=kpJRAAAAIBAJ&sjid=pGoDAAAAIBAJ&pg=1705%2C4055373 in The Pittsburgh Press (Monday, September 15, 1952), p. 20.
“Thank you for making this day necessary.”
The Yogi book: I really didn't say everything I said!, Workman Publishing, 1997, ISBN 0761110909, p. 10.
Said on Yogi Berra day in 1947 in St. Louis. By his account, he asked a teammate to write a speech, and he misspoke, saying "necessary" instead of "possible."
Yogiisms