Keeping on one's toes means to be alert, attentive, and ready to act or respond to a situation quickly. The antonyms of this expression would be phrases that denote the opposite feeling; relaxed, at ease, or inattentive. People who are not keeping on their toes would likely be less careful, less prepared, and more prone to making mistakes. The antonyms for keeping on one's toes include being laidback, carefree, and unconcerned. These words convey a sense of calmness and a lack of urgency, contrasting the sense of heightened focus and anticipation associated with the original expression.