He believes he's not as she sees him - she elivates him so high with her love, he is so afraid of risking her rejection, he falls back into the familiar facade of the safer, more familiar place he knows, unable to progress into the deeper love he feels he hasn't earned. Simply put; he wishes that he was half the man she thinks he is, but feels cowardace when he is so in love with her vision of him, he cannot truly open up to her, which perpetuates his insecurity as he feels even less deserving - feeling deceitful as well as the cowardace to reveal himself completely.