I Understand your battle as I have struggled most of my adult life until recently. Yes you should give in to your cravings it keeps you motivated. Yes exercise is key. Basic principles of weight loss you have to move more and eat less.(Not always easy). I had lots of back problems and eventually my dr. called me out on my weight and told me Im not helping myself by gaining weight. It was a wake up call I thought my life was over I had an MRI and I have an L5 disc issue that caused all the problems. I basically gave up and decided I was going to live the rest of my life in pain until my dr. called me out on my weight. At that point I decided that like you I was sick of the life I was living and needed to make a change. I took me 2 years but I lost over 65lbs Im healthier happier and yes my back still bothers me from time to time but with my dr.'s support and some medicine I work through it rather than sitting on my ass doing nothing and complaining. And those days of daily pain and suffering are long behind me and I will never go back to that person I was before. You can be successful you just have to be patient there will be ups and downs but if you don't give up you will perservere.