I believe they understood you. No, it is not normal. Going back to normal should be easy, and effortless.
What you're describing sounds like you've switched on something, and have trouble with a stuck "off" switch.
It should be as simply as sticking your arm into water. It's easy to just pull it right out. You'll notice getting your entire body out can be a lot more difficult.
Am I explaining this clearly? =\
If it is a disturbance, it is not normal. PhotoFocus is something natural with the human body, and is not something that should affect you with harm to your vision, even for a few extra minutes.
As far as my advice, I can't give much good at all, as I have not experienced this sort of thing. I would recommend retracing your steps with learning this step, and try different methods. Double check to see if you are doing anything wrong.
Remember, you can reference back to the book.
