on (one's) toes
Active, alert, and focused. Having two kids under age five sure keeps me on my toes! This attorney is known for using really deceptive and underhanded tactics, so be on your toes.
*on one's toes
Fig. alert. (*Typically: be ~; keep ~; keep one ~; stay ~.) You have to be on your toes if you want to be in this business. I have to stay on my toes to keep from getting fired.
on (one's) toes
Ready to act; alert.