Perhaps there are a couple of reasons.
First, you cannot see your head, so you don't fail in that. Everyone can notice this.
But perhaps you are expecting specific results, and you don't get them, so you don't continue noticing you cannot see your head... And if you don't continue, then it certainly won't do anything for you! If you say, "I tried that, but it didn't work for me", it means you are not doing it now, so it won't work for you!
How does that sound?
Yours,
Richard