I see this as a tool, and like any other tool if we dont use it, it won't work. We have this awesome tool that will help us feel full faster so we won't overeat. That been said, this tool is only one piece of the puzzle, we also have to exercise and choose the right foods for this to succeed.
I don't think the sleeve gives you discipline. Its a tool you use to help gain your own discipline. I find I still have to have will power to stay away from foods I KNOW I shouldn't eat, will power to limit the amount of carbs I take in, will power to limit snacking and when I do the discipline to make the right choices.
The sleeve is not a magic bullet. I find it does help me limit the amount of food I take in , and for that reason it works for me. I guess you must ask yourself.. why did all the other diets fail?