be on one's toes
keep on one's toes
stay on one's toes

The key was staying on his toes, alert at every moment of the day and night.

Here, we expect to stay on our toes until the last out.

I suppose one could also say that the magazine always tried to stay on its toes.

It was becoming a little complicated, and he needed to stay on his toes.

Sooner or later they'll catch up with us unless we stay on our toes.

I guess we just have to stay on our toes and hope for the best.

The group is not in any present danger, but stay on your toes.

He would just have to stay on his toes every second.

I want the two of you to stay on your toes during supper.

We'll only have a few seconds, so stay on your toes.