From Longman Dictionary of Contemporary Englishlet something slip (through your fingers)let something slip (through your fingers)to not take an opportunity, offer etc Don’t let a chance like that slip through your fingers! → slip
Examples from the Corpus
let something slip (through your fingers)• Colin, on the other hand, became discouraged and let things slip.• The Celtics let this one slip away slowly, painfully and needlessly.• Be careful lads not to let this one slip away!• Wrapped up with visions of kissing Deborah, I had ignored his bedtime rituals and let him slip away.• He held it up, and let it slip between his fingers.• And on most of the occasions when they had been alone together he hadn't let a chance slip by.• Attention creates the foreground of consciousness, letting the rest slip into peripheral awareness.• As an aside, the parties let it slip that the idea of a true playoff system had been scrapped. 