Carr specifically addresses this point in the book. He said that he was hurt to find out that after he'd published his book, and gave signed copies to friends, in the hope they would quit, many of his friends never even started the book. One of them finally admitted to him that they knew if they finished the book, they'd have to quit. So to prevent that, they just never started the book.
He also approaches the subject from the angle of timing, and that stressful periods may be more difficult, because stress is one of the triggers. Or at least we convince our selves it removes stress.
So I 100% agree that just like learning anything else you have to be willing to hear the information and process it without just dismissing it out of hand. Somewhat related is the Upton Sinclair quote, "It is difficult to get a man to understand something, when his salary depends on his not understanding it”.
I totally went in with tons of skepticism. Here's some huckster telling me theres a secret way. Yeah, ok. But I guess after reading enough of it, I started to realize that I had become really good at coming up with excuses, and that skill was being used against me to keep smoking. In my view, he made a persuasive argument, and wasn't trying to sell me more shit. By the time I finished the book, I was completely convinced that he was correct, even though I had not yet had my last cigarette.
I also read the book over two days, so I really got the whole message in a short amount of time, as opposed to reading a page or two a day for six months.