I think there are a gazillion reasons for weight gain and a gazillion reasons/ways to lose it.
You'll succeed when you find your recipe for success.
Carb reduction works best for me, though I hate it, and for WAY too long, I have been trying to convince myself that I wouldn't have to carb-restrict if my motivation and willpower were stronger.
Yeah, so much for that theory, I haven't lost in months (except when I go back to low carb).
I don't want to low-carb forever, but that may be the only way to get and keep the weight off. I will have to decide what's more important to me, toast and pasta or a fitter body.
For me, the weight itself doesn't bother me at all. If I could get healthy and fit enough to be as active as I want to be, free of pain and meds without losing weight, I wouldn't bother trying. Although my first 20-30 lbs were without trying. Weight loss wasn't my original goal, it was just a side effect of working at getting healthier.
I think there are too many factors to weight loss success to reduce it to a simple matter of attitude or belief. I think it's a lot more complicated than that.