There're a few tricks that may help to eliminate the fear:
Prepare yourself as well as possible when faced with a particular situation or atmosphere.
Preparation already means half success. Readiness means there's nothing to fear anymore.
Fertilize and build confidence. Do something that can add to your confidence. Confidence will arise if, for example, you're sure to have skill that no one else does. If you're surely proficient in karate, show the capabilities.
Having raised confidence, thicken your belief. Believe, you can do it. Belief is the energy or driving force to deal with any situation.
To increase confidence and belief, you must add a skill or expertise through training or studying in earnest. Expertise can be controlled as long as you're diligent and industrious. Skills and expertise that you've achieved, by itself, will increasingly eliminate your fear.
Face and do what you fear, then it'll disappear. The fear is totally imaginary. Why should you be afraid of something that's not necessarily happened?
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