When you lack faith there isn't enough power and positive energy being sent.  One week isn't enough time to really get confirmation and, as I told in my PW book, I was just lucky that I was lying next to John when I first used the technique.  Had I not been I would never have known how powerful the visualization was and that he received EXACTLY the message I sent.  But when you have doubt you may be half-ass as far as the visualization because in the back of your mind you are thinking it isn't working.  :-)