Rules & Our Brains

I have been a scholar for a few years now and have used the Stop Overeating Course and Masterclass in order to stop overeating and lose weight.

It works perfectly whenever I set out a protocol and follow it and I have done so already for 3 rounds since I joined, only to find myself gaining all these 45 pounds back.

I spoke with two friends yesterday: one who stopped smoking entirely and one who started Bright Line Eating a year ago, where her rules are that she doesn’t ever eat flour and sugar.
Both always abide by the rules that they decided for themselves and never touched a cigarette or flour and sugar, respectively, with great success.

Knowing as much as I already know from Brooke’s teaching, I could see how beneficial it would be that a human would set out a rule and then the brain will just follow the new plan and wouldn’t even suggest (urge) to touch that stuff.

I wonder what could it be that I am doing differently that MY brain doesn’t “buy” into the idea that it’s a non-negotiable rule, like my friends’ brains do.
My experience has been different, and from reading questions here I see that some experience something very similar.

Are certain brains resistant to believing and embracing new rules while other brains embrace them immediately?