Decides on is a common phrase used to describe making a choice or determining a course of action. Antonyms for this phrase might include indecisiveness or uncertainty. When someone is indecisive, they may struggle to commit to a decision or course of action, instead vacillating between different options. In contrast, being certain or resolute can be the opposite of indecisiveness. Other potential antonyms for "decides on" might include postpone, delay, or defer, which all suggest delaying a decision or action for a later time. Ultimately, the choice to decide or not decide is a personal one, and the best course of action will depend on the specific circumstances at hand.