I don't get it, either. I never did come to understand how it works. But you have to come to a sincere, in-your-gut realization that your spouse is capable of believing it, at least for now, even if you can never really understand how they could do it.
Because if that's the way he's thinking, and you're still thinking of him as a man who wants sex in the marriage, you can't help but go back to trying to figure out how you're inadequate. Even as you think it, you will sometimes think to yourself that you're not making any sense, but you'll still think the same things.
The other thing to remember is that it's just as hard for him to understand why sex is so important to you as it is for you to understand how he can go without it. His way of thinking seems to him the natural and maybe only way to think . . . just as yours seems to you (well, and me too.) In my marriage, I was trying to figure out why my wife would pretend that her sex drive was completely gone . . . and all I could come up with was that I wasn't attractive enough for her, and maybe I never had been--maybe she had lost her passion for me, or maybe she'd been faking it in the early days, knowing that she didn't want a sexual marriage but knowing that most men wouldn't accept that. At the same time, she was either avoiding thinking about our sex life because she doesn't enjoy confusion and guilt, or on the rare occasions when she thought about it, she was wondering why I would pretend that sex was this huge issue--what was I really upset about? Was it that she wasn't enough for me and I wanted out? Was it just that I thought I'd made a mistake marrying her? She didn't know, but she knew no one would really be so furious over a simple physical release like getting laid.
We didn't understand each other, and we tried to read each others' minds.