It ain't over till the fat lady sings
Meaning
Nothing is irreversible until the final act is played out.
快樂是要蓋棺才能論定
Dan Cook made a closer stab with "the opera ain't over till the fat lady sings", in a televised basketball commentary in 1978. Cook was preceded however by US sports presenter Ralph Carpenter, in a broadcast, reported in The Dallas Morning News, March 1976:
Bill Morgan (Southwest Conference Information Director): "Hey, Ralph, this... is going to be a tight one after all."
Ralph Carpenter (Texas Tech Sports Information Director): Right. The opera ain’t over until the fat lady sings."