You’re probably making a better first impression than your brain is telling you.

You are the only person in the room with access to your own nervous system. Everybody else sees a reasonably normal person talking, while you get the full broadcast of the shaky voice and the thing you said wrong, and you then assume the broadcast was public. It almost never is.

The cure is evidence rather than reassurance. After something you think went badly, notice what actually happened next: whether people kept talking to you, whether anybody mentioned it, whether you were invited back. Take that as the real data and let your own commentary be what it is, which is a worried guess.