That's the question I hear everywhere. First off, don't lose weight, lose fat. Muscle, bone, and guts have weight to them, you certainly want to keep that kind of weight. Set realistic goals, and track them religiously.
Excess fat is stored emotion. Usually, fear. It's a manifestation of negativity, we're wearing our painful past when we put on excess fat. We're weighted down by the gravity of our situations. We store out "issues in our tissues." To get lean, forget the past, move on and move into a new you. Forget your story, and make a new one. If you think losing weight is only about calories in versus calories out, you're missing the big picture.