This is a great point. People are mimetic in conversations and will respond to how the other person presents. If you feel uncomfortable, they will too. And almost all of it is tone and body language, not the content of your words. I wish I'd figured this out at a younger age. I spent years afraid of talking to anyone and it held me back. To the younger people here - it gets better. You learn to be less hard on yourself, and more fluent speech follows.