Focus must shift to quality nutrients and other environmental factors such as sleep, stress, smoking etc , instead of a desired weight or size. Numbers are just data and the measure of the result of the behavior. The behavior is an action in which can and must be controlled.
Your bodies composition is defined as your fat in your body proportionate to your lean mass. It is not possible to control that, once again, it is only possible to control behaviors. You must work to create the behaviors that lead to lipolysis (fat burn) as well as an increase in lean mass.
Sporadic burst of activity such as dieting are not effective. Behaviors that achieve and maintain healthy body composition take a lifetime and become easier to maintain overtime. Realistically it is a lifetime of consistent and repetitive behaviors that lead to long term weight loss.