on your toes idiom
C2 忙个不停，永不懈怠
Someone or something that keeps you on your toes forces you to continue directing all your attention and energy to what you are doing.
I work with people who are half my age so that keeps me on my toes. 我和只有我年龄一半大的人一起工作，所以一刻也不能松懈。