If you gave all your self-doubt a face what would it look like? Get a face in your mind… now start calling it really mean names. Be the worst bully on the planet and call your own self-doubt names, make it cry.
What names do you use. Think about them. Some of them will reflect how you really feel about your own negativity. How much of your self-doubt can you get rid of just by realizing how untrue, foolish, etc. it is.