A childhood belief about speaking

I used to be confused no end by the use of the phrase "You never can tell". It seemed to imply that the outcome of an event being spoken of would remain a mystery forever, no one EVER knowing the result. But generally the phrase was applied to matters whose outcome would actually soon be obvious. I eventually figured out that the intended meaning is that you can never tell IN ADVANCE about such outcomes, but only after a whole lot of confusion in thinking that "never" always meant never, forever.