I recommend watching the video but I'll try to explain, as it's not so cut-and-dry. He postulates that fragmentation within the mind makes it harder for us to avoid and resist temptations, because the effort of masking the parts of us that have been fragmented or compartmentalized, takes away from the effort required to combat the temptations. So reducing fragmentation allows more energy to be allocated towards avoiding and resisting the temptations.

The fragmentation is caused by you wanting the late-night food, but knowing that you shouldn't eat/order it. Your 'ideal' state is at odds with your 'desire' state, and the effort of that conflict makes it easier to ultimately succumb to the temptation. And after you succumb once, it's easier to do so each subsequent time you feel the temptation.

So it leaves in a conundrum where if we resist we're screwed due to further fragmentation, but also screwed if we yield to the temptations (and end up eating late-night junk food every night) because this too causes more fragmentation. So his thesis is 1. try to avoid the temptation altogether (i.e., go to bed before the late-night cravings hit), and 2. change your ideal state to be less at odds with your desire state - instead of beating yourself up about feeling the temptation, recognize that the ideal state is not fixed, and it in turn requires less effort within the mind to fragment those conflicting states, which leaves more energy for you to avoid and resist the temptations that still arise.

So it's a continuous process to reduce the existing fragmentation so that it in turn reduces the temptations you feel on a regular basis.

For me, it's relevant to my smoking habit. I know I shouldn't do it, and I feel a deep guilt and shame whenever I do. Yet I keep doing it (both due to chemical dependencies and the habit I've cultivated over the years) - the desire and disdain I feel simultaneously around the same action results in fragmentation. That guilt and shame from the fragmented sense of self (am I a smoker or am I not) leads me to want to smoke more (more fragmentation --> more temptation). Which then leads to more guilt. And the downward spiral continues.

He says, if you step back and recognize that a sense of self isn't so rigid, the fragmentation starts to break down. I don't have to feel bad about a temptation if I allow myself to be both a smoker and not a smoker vs. one over the other. Through introducing flexibility and forgiveness into my sense of self, the fragmentation and subsequent temptations seem to diminish. It's not a cure by any means, but it is a new perspective that I personally can see some value in adopting.