The phrase "fix upon" refers to making a decision or choice after careful consideration. Its antonyms are "hesitate," "waver," "vacillate," and "indecisive." These words imply a lack of clarity and determination in decision-making. For instance, someone who hesitates may be uncertain or conflicted about what to choose. Similarly, waver and vacillate suggest a lack of steadfastness, where the decision might change depending on circumstances. Indecisive describes someone who is unable to make a final determination. The antonyms of "fix upon" emphasize the importance of making clear, definitive choices and avoiding indecisiveness.