Antonyms for the phrase "thinking better of" can vary depending on context. If we're talking about a decision, antonyms include "trusting one's instinct," "doubling down," and "sticking with one's original plan." For a behavior or action, the antonyms might be "persisting," "following through," or "committing." These opposite actions suggest that instead of rethinking or reconsidering, one should move forward with confidence or steadfastness. However, if "thinking better of" refers to changing one's mind due to an improved understanding of a situation, possible antonyms may include "stubbornness," "closed-mindedness," or "ignorance." In this case, these opposites suggest a lack of willingness to adapt or learn from new information.