Any non-understanding partly comes down to Affirmations turning almost into an industry, another chance for people to write books, web articles or make movies about it. Confusions arise - too many words. People successful in their fields affirm naturally.
Fact is, such "rules" or methods could be got onto a sheet of paper with maybe some guidance with visualisation (if appropriate) on another. It isn't complicated - that's the whole point. Affirmations should be doable anywhere, anytime a few moments allow.
The three pitfalls are seekers being impractical, losing motivation when results aren't imminent, and searching around for results rather than just let them happen and note when they do.
I have to admit I abandoned the video almost at once. This "You create your reality" came up as the title... well, pretty obvious, that - but then underneath "What God told me about the law of attraction," buttoned it up for me. It's one of the problems of New Agey stuff, too comparmentalised and yet creeps about from subject to subject. The law of attraction (that I think is basically nonsense) is quite different from Affirmation...hence the confusion I spoke of in the opening of this comment.