Your character is like handwriting. Nobody else can fake it for long, and it shows in every line.

Character comes through in small consistent ways nobody is deliberately producing, which is why it cannot be faked for long. A performance needs attention, attention lapses, and the pattern underneath reappears in the details. People read that pattern without ever putting it into words. They simply come away with an impression that turns out to be right.

Pay attention to the parts of your behavior you do not think about: how you answer when rushed, what you do with a mistake nobody saw. That is what is being read. Change it there rather than in what you say about yourself.