The opposite of "most flustered" could be "composed," "collected," or "calm." These words suggest a sense of relaxation and tranquility rather than anxiety and confusion. Someone who is composed is in control of their emotions, regardless of the situation, while someone who is flustered is easily overwhelmed. When you are composed, you are more attentive and can think more clearly, while being flustered makes it difficult to focus on anything other than the source of your anxiety. Therefore, acknowledging and addressing the cause of your feelings can help you move from flustered to composed, thereby improving your overall well-being.