Definition
This idiom is used to emphasize that many things can go wrong or change before a plan or intention is fulfilled.
功虧一簣
They thought the deal was done, but I know there's many a slip twixt cup and lip.
他們以為交易已經完成，但我知道事情在完成前仍可能發生許多變故。
They thought they had victory in the bag, but there's many a slip twixt cup and lip, so the game isn't over yet.
他們以為勝利在望，但事情在完成前仍可能發生許多變故，所以比賽還沒結束。
Even when everything seems to be going smoothly, don't forget there's many a slip twixt cup and lip.
即使一切看似順利，也別忘了事情在完成前仍可能發生許多變故。