It's most likely that it is not true. And, when you tell yourself someone is scared of you, it will only make them more scared. This is just the way it is. If instead you say to yourself, "im sure this person is not really scared of me. If they are, there is probably something wrong with them, because i am certainly a nice person who would never intend to scare or hurt anyone. I know i am not perfect, and i may sometimes be misunderstood, but that is no reason for somebody to be scared of me."
Something along those lines is what i would tell myself. Again, telling yourself, and worrying about being scary will only make more scary. Try to distract yourself from those unhealthy thoughts.