Hi BMFFM,
To begin with relax, and go easy on yourself. Please, stop convincing yourself and ultimately attracting to yourself that you will start focusing on the page.
Paul mentions lot of tips to maintain the Photo Focus and chief among them are:-
1. Let go of distracting thoughts
2. It could be the case that you are turning the pages slowly. Try turning the pages at a little faster rate, but not missing on the rhythm.
3. Pay attention to your feelings and appreciate them.
Further what you can do is, instead of looking right through the book, try looking a little above the top edge of the book and at the same time noticing the four corners as well as all the whitespace in the book.
I hope this helps. God bless you.
Kind regards
Vaibhav Sharma