Definition
This idiom is used to emphasize the uncertainty of events; many things can go wrong before something is completed.
功亏一簣
They thought victory was assured, but there's many a slip twixt cup and lip; they lost the competition in the end.
他们以为胜利在握，但世事难料，最终他们输掉了比赛。
I thought the deal was done, but there's many a slip twixt cup and lip, so I am still waiting for final confirmation.
我以为交易已经完成，但世事难料，所以我还在等待最终确认。
She was so close to getting the job, but there's many a slip twixt cup and lip, so she must ensure she is fully prepared.
她差点就得到了那份工作，但世事难料，所以她必须确保自己完全准备好。