They schedule their work-outs, their diet and are sensible with their lifestyle choices. Additionally, their lives appear more balanced. The happier ones play sport outdoors, swim at the beach or go hiking. The successful ones talk to fitness coaches, research online and read books to find new ways to challenge their mind and their body.
It really is about lifestyle. You can't lose or gain weight just by observing strict rules at a gym and watching what you eat. There's an attitude of patience, persistent work and eagerness to learn behind the winning ways of people with high fitness levels (and low body fat.) The human body is built to endure. It needs to be challenged, nourished, pushed to the limit and then rested. There is no easy way out.
As to methods there may be a million and then some, but principles are few.
The man who grasps principles can successfully select his own methods.
The man who tries methods, ignoring principles, is sure to have trouble.
Ralph Waldo Emerson