Generally, scientific researchers - say those studying the universe and how it works - don't shoot directly for a grand goal. They focus on bite-sized problems that seem relevant and solvable. This methodology usually pays off, and the scientists are able to make small steps toward solving the fundamental questions.
Losing weight works the same way, doesn't it? The best thing to do is begin by solving some smaller issues related to weight problems. For example, instead of trying to solve the big picture, "why can't I lose the weight", Janie started small by asking herself "why do I always go off my weight loss diet when I visit my sister?"
Janie addressed this circumscribed problem, and she was able to come up with answers and solutions that were very workable. She kept at it, and after a time, she no longer went off her weight loss diet when she was with her sister.
So, if Janie can proceed this way, tackling her "bite-sized" weight problems, they will add up, won't they? Each smaller weight problem solved will be a step toward the ultimate weight loss goal - solving the "why can't I lose the weight problem." All the in-between steps will make up a path to that grand weight loss goal.