From Longman Dictionary of Contemporary Englishit’s now or neverit’s now or neverCHANCE/OPPORTUNITYused to say that if someone does not do something now, they will not get another chance to do it Quite suddenly, her mind was made up. It was now or never. → now
Examples from the Corpus
it’s now or never• Twoflower, I thought, it's now or never. 