I think you're describing a rather common form of superstition, fearing that acknowledging a fear by saying it aloud, will somehow, magically, make it more likely to happen. And isn't it odd that we seem to ready to believe that, whereas if someone said that to walk around saying that you were going to win the lottery would make you sure to actually win it, we'd think they were an idiot ( if it were that easy, surely everyone would win ? )
Indeed, almost the opposite is true. So long as we're scared to acknowledge and face our fears, the more they lurk around in the shadows at the back of our minds, growing more fearful all the time, and the more one confronts them, admits them and shines the light on them, the more we can see them in proportion and begin work on getting rid of them.
Admitting such fears won't harm you at all, though it's best done with the help of a counsellor who can help you to confront and beat them. What may be happening is a slightly different thing, the self-fulfilling prophecy. If you convince yourself that you won't and can't get that promotion, then you will communicate failure to those assessing you for promotion --- you'll look and walk and talk like a failure, you won't try where you might, and you'll be bound to make a much lesser impression than you are capable of --- and THAT, can reduce your chances of success. It's not the speaking of the fear, but the self-sabotage that can make it come true.