When people go on a DIET they tend to do it short term without even realizing it - Most of these people have reasons: I have a wedding in six months, I have a reunion, I am going to a big event etc... They don't look at it as a long term goal they just want fast results never thinking of the true value of what they could be learning along the way.
If you look at your weight loss as a journey rather then a DIET you will be better off in the end.
What is a diet? Diets are a way to loose weight, maintain weight, maintain good health and for this wouldn't you want it FULL TIME instead of part time. If you are going to go through the trouble of learning how to eat better, watch what you eat, read labels, eat less, eat more healthy foods and in the end be able to buy that dress or suit you wanted, be in that picture and stand in the front, dance with the crowd and feel first-rate why not keep it off for good. So many people go through the motions not realizing they are learning how to eat better and how to create better patterns and habits.
Most people go on a DIET and then go off the diet - how about going on a WAY OF LIFE - If you look at it as learning how to make better choices instead of doing it just because you are on a diet you my find that you have created a way of life and not just a quick fix.
If you join a weight loss group and write down what you eat - Keep those items and look back at them when things are rough or you are falling off track to see what you ate that helped you stay on track and loose weight, if you eat on a food plan ask yourself what did I eat then that I don't eat now, you don't have to join that group again but you can make the same kinds of foods, find them in the food stores just be conscience of it.
A good trick is when you loose that weight and are feeling really good - THROW OUT YOUR OLD CLOTHS that do not fit any longer because they are too big, this will entice you to purchase new and exciting cloths and keep you on track so you cant go back - Kind of a tough love with a feel good result.