How sincere are we to ourselves?

How sincere have we been to ourselves? I doubt I am. Herm..yeah.
The first time I heard the notion of trying to find the sincerity in oneself was from my boyfriend. I remember asking him about why is it he seems to be very active, becoming club's presidents, school perfects, state's rep for marathon... Yet, he wasn't all that when I met him. Mind you, I only really, really know him at during the final year of our college life.