“There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
There is another theory which states that this has already happened.”
― Douglas Adams, The Restaurant at the End of the Universe
Actually more appropriate is the monster ,(forgot its name) described/created by the same author. Anyway the monster believes that if you cannot see it the monster itself cannot see you.
So the best defense against it, is to close you own eyes
[Edit]
The Ravenous Bugblatter Beast of Traal is a wild animal from the planet of Traal, known for its never-ending hunger and if you can't see it, it assumes it can't see you.
if the Guide is to be believed. For, according to the Guide, draping a towel over your head will confuse the beast long enough for one to make a quick getaway. This is because (as mentioned above) the philosophy of The Ravenous Bugblatter Beast is that, if you can't see it, it can't see you.