Sure oneself is an expression that denotes self-confidence and assurance. Some of the antonyms that can be used to describe the opposite of being sure oneself are doubtful, unsure, hesitant, self-doubting, diffident, insecure, and uncertain. Being uncertain about oneself and one's abilities can lead to anxiety and lack of conviction, which in turn can impact one's personal and professional life. Feeling unsure can also make it difficult to make decisions and take action. Therefore, it is essential to cultivate a sense of self-assurance and confidence to succeed in life. By recognizing and addressing the opposite of being sure oneself, individuals can work towards building a healthy sense of self-esteem and instilling confidence in their abilities.