to stay active, alert, and focused on something or someone and prepared to deal with problems might happen
忙个不停，忙得不可开交；警惕，警觉；集中注意力，不懈怠，作好行动准备
常用组合be on one’s toes / keep on one’s toes / stay on one’s toes / keep one on one’s toes

例句：

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。

Having two kids under age five sure keeps me on my toes! 有两个五岁以下的孩子真使我忙得不可开交！

You have to be on your toes if you want to be in this business. 如果你想在这一行干下去，你就得时刻不懈怠。

I have to stay on my toes to keep from getting fired. 我必须保持积极性以防被解雇。

Surprise visits help to keep the staff on their toes. 突击巡察有助于使员工常备不懈。

This attorney is known for using really deceptive and underhanded tactics, so be on your toes. 这位律师以使用真正的欺骗和不诚实的手段而闻名，所以你要特别小心。

Your spelling is wrong. You wrote “practise” but it should be “practice”.
你的拼写有误。你写了”practise” ，但应该是”practice”。
Oh! Thanks for keeping me on my toes.
哦！谢谢你提醒我。