Sentence:  You have to think of yourself as an already amazing person who's hiding behind extra weight—a superhero in a disguise. If you follow the program, ... change the message from “I'm a big loser” to “I'm a big weight <WSD>loser</WSD>.” 
Meaning of the word marked with <WSD> tags:  One who or that which loses something, such as extra weight, car keys, etc.