Hi there!
Oops! Didn't mean to confuse anyone with my post (and i didn't make myself too clear either - sorry!). Try checking out a basic science text. (or read 'Eye and Brain' by ? - it's quite fab).
A better way of saying it would be to point out that when you are looking through a dirty window the dirt goes blurry. However, when checking out a magic-eye picture you can still make out the original pattern. The latter example is what i think is required for p-focus.
Either way AlexK (and everyone else) is spot on when they say that all you need do is relax. I also find books with smaller margins are easier too.
Hang in there.
Nick 
