Diet breaks are essential, far too many people think they can skip diet breaks and just "push through" with will power etc, i used to be guilty of this my self in the past, skipping diet breaks ALWAYS backfires, Not only dose it make the PSMF hell but it makes sticking to maintenance after the diet just as hellish and near impossible. and its the reason so many people find them selves regaining weight.
i used to think i only need a few days break to satisfy my cravings and ill jump right back into it only to learn the hard way it doesn't work like that. You need a prolonged diet break for everything to normalize again for cravings to return to normal etc, I don't know what physiological stuff is going on during this time but i know from experience from the way i feel. At this point i can tell when i need a diet break and when i am ready to go again, its something that comes with experience.
Diet breaks are also important to learn how to eat at maintenance, and not just finish PSMF go and eat all you want for a few months only to then think i need to diet again because i got fat. Yo Yo dieting is the worst thing you can do to your body, you want to reduce your weight, maintenance your new weight for a while, and repeat until you are at your goal weight.