In order to change chronic eating habits, you need practice. There's no other way.
Let's say you are chronically overeating, even when you are on a diet plan and that's what prevents you from being a weight loss success story. So...can you just quit overeating?
No - and the reason is, because you practiced your way of eating over and over until it became automatic. Now it's the thing to do in your life.
In order to change this eating habit, you need to institute some changes to your eating behavior and practice, practice, practice.
Start out with a small change and do it over and over until it becomes less strange and feels more natural. Then you can move on to another small change, until that one becomes more natural.
We are all creatures of habit. It's a question of gradually replacing bad habits with good habits. It's not the easiest thing in the world to do, but if you want help losing weight, this can produce results. (Make sure to check with your physician about what and how much you should eat before making any changes.)