Hello Caz. I think the answer to the question is that diets in general are letting you down. They just don't work in the long term for most people, and they seem to cause so much misery and yo-yo weight gains and associated health problems.
Maybe it's just time to draw a line under the dieting concept altogether and decide that you're going to embrace a relationship with food that you can comfortably sustain for the rest of your life, not just while you lose weight. I really do think that cutting out the short term thought patterns and behaviours is one way of finally getting a real handle on the food demons.
Doesn't have to be about starvation or punishment, just good portions of good food, regular treats, heaps of fruit and vegetables, and a resolution to be patient and kind to your body and mind, and nourish them properly for life.
If you don't regard it as a diet, but more a positive shift in how you live, then you can't fall off the wagon again and you can't fail!