You have a job interview. Before you go, you keep telling yourself you won't get the job, and chances are, you won't. If you tell yourself you will do terribly in the interview, you probably will. If you continue to tell yourself what you are going to do, how you are going to act, and what is going to happen, be prepared for that to happen. If you are letting your anger, insecurities, negativity, etc. lead you and make your decisions for you, you will have a negative outcome.
Teach yourself to change your thought patterns from unwanted behavior and outcomes to desired behavior and outcomes. Tell yourself, "I will do awesome at this interview." Tell yourself, "I'm going to rock this interview, get this job and be great at it." or "They will love me".
You are telling yourself what will happen, who you will be, and how to deal with your feelings when it all comes down. If you start telling yourself negative things before they happen, you will perceive them in a negative way.
You are who you are because that's who you say you are.
Tell yourself things like, "I can." " I will." " I am awesome!" Then go with flow. Face every day, every person, every situation with hope and an open mind. You will never know the outcome. You may be super surprised! If you aren't satisfied with the outcome, you may start to notice how you have changed your behavior towards the outcome. You may start to see that you are happier, more accepting of what is , and find it easier to move on.
In the words of En Vogue, "Free your mind, and the rest will follow."