Getting on a diet and losing weight is one thing. Keeping yourself on that diet for life is another. We eat eccessively because of comfort. It's comfortable to us who to eat more than our body needs and this causes many health problems. It's no different than anything else that has to over work. At some point the machine is going to break down. It acutually gets tired.
Changing this habit of overeating has to be one the hardest lifestyle changes in existance for people who just love to eat. I see the looks on countless people's faces when I mention the word "diet." They treat it like work, and by perceiving your lifestyle change this way, it's bound to fail. Not many people realize overeating is a habit. You can definately change habits. The question is how do you change this habit effectively. You succeed at the little steps.
There are two phases to this lifestyle change. The first phase is getting your body and diet to a certain level. The second phase is maintaining this level for life. In the second phase you have to create a perception which is different than the first. In this phase it's all about living the diet, not following the diet. You have to set up the scenario in your mind this is your life now and this is how I live and eat. It becomes a part of you no different than any other perception you choose to have about life. It's exactly about what you expect to see in the mirror every day.
The small steps you take every day will lead to the ultimate desire of acheivement.