( saying ) nothing is completely certain until it really happens because things can easily go wrong
THERE'S MANY A SLIP 'TWIXT CUP AND LIP
Meaning of THERE'S MANY A SLIP 'TWIXT CUP AND LIP in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005