there is many a slip twixt cup and lip
there's many a slip twixt cup and lip
proverb Even something that one feels confident will succeed can have disastrous problems before it concludes. "Twixt" is a shortening of "betwixt," an archaic form of "between." Everything seems to be going smoothly, but there's many a slip twixt cup and lip, so don't lose focus until we're over the finish line.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
there is many a slip twixt cup and lipLITERARY
If you say there is many a slip twixt cup and lip, you mean that plans often go wrong before they are completed so you cannot be sure of what will happen. The building is due for completion in September, but as they say, there's many a slip twixt cup and lip. Note: People sometimes just say there's many a slip, or change the second half of the expression. But there's many a slip twixt now and the eight or nine months it will take the company to design and reopen a new café. Note: `Twixt' is an old-fashioned word meaning `between'.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012