On your toes
Meaning: alert, attentive, prepared for difficulties, someone or something that keeps you on your toes forces you to continue directing all your attention and energy to what you are doing
Example: He was on his toes and produced a very good impression on them. I work with people who are half my age so that keeps me on my toes.
Example: He was on his toes and produced a very good impression on them. I work with people who are half my age so that keeps me on my toes.