Yogi also said that "Half the lies they tell about me aren't true"

"I didn't say a lot of the things that I said"

"It ain't over 'til it's over,"

"You can observe a lot by watching."

This is the essence of "You don't know what you don't know," only it's being expressed in a comical way, much like Yogi Berra might have said. (To those unfamiliar with the Yogi Berra reference, he was a professional baseball player who was reknowned for his wry way of saying things, such as, "It ain't over 'til it's over," and, "You can observe a lot by watching."