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

At first I didn't know what the growth on my toe was.

He was still just above my body, on hands and toes.

They're going to go out of their way not to step on our toes.

Get the kids in and keep them on their toes.

For a moment they stood, moving a little up and down on their toes.

She stood on her toes to see over people, and called out.

I have to be on my toes all the time.

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

How does he know you guys up here are on your toes?

Little Will stood on her toes to see who the boys were.