Your statement can have multiple interpretations. I assume you mean this one: Your fear will be a self-fulfilling prophecy; to prevent that, stop being afraid?
Of course that's like telling someone who is depressed, to "just be happy".
I think he means that thoughts have an actual effect on the unfolding of the physical world.
Which is a "self-fulfilling prophecy", also known by a new-age term as "manifestation".