Let’s say you are in a supermarket and encountering someone who is being rude. Often people do not say anything to that person because they are afraid of a potential confrontation. You may fear the situation will devolve into a physical confrontation, or that the rude person will say something and you will not know how to react.
Maybe you have a tyrannical boss and you do not know how to talk to them in a reasonable manner because you expect them to be unreasonable. In that situation, you need a strategy. You need to have a plan prepared and rehearsed to reduce your stress at work because you know that conversations with that boss are inevitable.
Give it some real thought and write it down. Think through what you are actually afraid of. Is it how you will react? Is it how the other person react? Try to put yourself in their shoes and understand their perspective. How does understanding their point of view change yours? What would happen if you did confront that person? Consider potential outcomes and plan your response accordingly.