No...it's not necessarily a lack of discipline. For example, if you tried to put me on a low-fat, high-carb diet, within about three days I would feel sick and exhausted (I've tried them). If someone like me goes off such a program, it's good common sense, not lack of discipline.
Another example is that I used to walk almost two hours a day because I did dog rescue and I had up to five dogs to walk (and for various reasons I had to walk them two by two). Anyway, I did this for a number of years and lost no weight, even though I was overweight. Then, I cut way back on grains and sugars, and I slowly lost 20 pounds with no dieting or extra effort.
Calories in/calories out are not the only things that effect weight.
I think that you will always be one of those folks who simply will not get it. Exercise and eat fewer calories seems out of your realm of reality. You will try all sorts of different diets, have a million different reason for failing....all the while not understanding such a basic simple technique of eating the SAME kinds of foods you always eat, but fewer of them....and exercising, knowing that exercise will increase your appetite, which will involve DISCIPLINE to NOT eat more calories.
It's too simple to grasp for you, dear.
Sorry I wasted your time.