keep someone on their toes 保持警覺、小心謹慎

走路時隨注意著腳趾(toes)代表著隨時保持警覺、小心謹慎之意。類似的成語還有keep your eye on the ball。

definition: If you say that someone or something keeps you on your toes, you mean that they cause you to remain alert and ready for anything that might happen.

例句

1.With the quiz on every Monday and Friday, the demanding teacher keeps the students on their toes.

2.The unexpected warning has undoubtedly keep the investors on their toes.