Self-fulfilling prophecy

I had a random thought while I was laying in bed last night, which comes down to this:

Your mindset is extremely important when it comes to lucids. If you believe something is not possible, you can't make it happen. Then I wondered, how do we know for sure that a lucid will fall apart if we become too excited about being lucid? What if that only happens because we have been told that that's what will happen and now we're expecting it, thereby creating a self-fulfilling prophecy? I remember reading about Stephen LaBerge coming up with a similar question, only it was about the idea that a dream would stop if you said your own name, if I remember correctly.

How do other people feel about this?

This believing thing goes for many things, not only dreams. You will most probably fail in anything if you don't believe you can do it.
The excitement brings up some body impulses like rapid heartbeat, sweating, fast breathing so it's basically like a physical attempt to wake you up. I think in this case the cause is more body-based than presumptions or anything.