Do what you're afraid of
One of the main reasons for fear is the unknown. The more unusual the situation is for you, the more afraid you are. It turns out to be a vicious circle: you avoid certain conditions, so you don’t get used to them, so you are afraid. To break it, you have to take a risk.
Action Plan : Does public speaking make your hands shake with fear? Raise your hand more often in class, take reports, and at the same time ask to be the presenter of some event or go to a theater club. Are you afraid to make phone calls? Call somewhere at least once a day: check opening hours, ask questions about the assortment.
Result : At first it will be scary, but gradually your communication skills in circumstances that frighten you will improve. You will act automatically, and at the same time you will see that you will encounter a negative reaction very rarely, if not never.
Come up with answers in advance
Self-doubt appears due to the fact that you do not know how to act in a given situation. What if you mispronounce a word and everyone laughs? Or will the cashier be rude to you because you don’t have change?
Action plan : We all love to replay a conversation that has already passed in our heads and come up with better arguments. So why not do the same thing, just with hypothetical situations? Imagine that the worst thing has already happened, and you need to react somehow. Remember the best lines, they will come in handy later. You can even write it down in a separate notebook with headings: “for quarrels with the seller,” “if you were rude on the phone,” etc.