If you were mistaken, it means you made an error in judgement, assumption or belief. Antonyms for this phrase would be accurate, correct, right, true, exact, precise, and perfect. These words denote that something is correct or factual without any mistake. When you make a correct assessment of a situation, you are not mistaken. Similarly, if your knowledge of something is precise and factual, you are far from being mistaken about it. In essence, the antonyms of "wert mistaken" highlight accuracy, truthfulness, and correctness, which are paramount to ensuring that we do not miss our target in whatever we do.