I am a life long dieter who understands where you're coming from. It's not like I don't know how to lose weight. I can cite the calorie and fat content of the majority of foods, I can compute BMI, TDC, and BFR in my head. I'm an expert dieter! But I was overweight for years and years.
For me it was about my mind. I was depressed, unmotivated, stressed, and overwrought. Short term diet programs worked but were not sustainable. When I had a bad day I would soothe my emotions by eating chocolate. It wasn't until I started to learn how to clear my mind that I actually became mentally equipped to lose weight.
Let me say, I'm no expert. I still indulge in the wrong foods sometimes. I still let the stress tell me that I deserve a peanut buster parfait from time to time, and I still want to lose another 20 lbs. But most of the time I eat well (I'm a vegetarian now, but not because of weight loss), I do the little things that bring activity into my life (stairs vs elevators, parking at the farther reaches of the parking lots, etc), and I don't "diet" any more.
I don't know if this would work for you, but the clarity of mind that comes from meditation and visualization, journalling, whatever it takes to get in touch with what's going on inside really helps. And I totally agree with the PPs about taking it slow, don't look for a quick fix, and make small, smart lifestyle changes that will bring you closer to your goal. And BTW, your goal should be the first 5 lbs, not the whole 80

And the best part is.. when you lose that first 5 lbs reward yourself!! You CAN lose weight, but forget the diets, find changes you can make that will last a lifetime.