Do you feel afraid or nervous while arguing with someone and how did you fix that?

You have to truly believe the things that you say. Don’t insult them directly as a person because it will make them do the same; actually keep the argument objective and on-topic. Also, in my experience it actually helps TO look directly at the person, because it lets them know you are confident in what you’re saying. If you keep a level tone, it gives them the impression you are winning the argument, even if you are nervous.