'Honestly express yourself' is one of the core belief of Bruce Lee, who, in his Lost Interview DVD (Bruce Lee: The Lost Interview) consistently encourages. For him, honestly expressing yourself means being honest with your true intentions and thought processes and displaying this through your actions.
An example he uses to illustrate this is through expressing yourself in such a way that when you would are thinking of punching, you punch, when you're thinking about kicking, you kick, and not necessarily doing anything else.
How I see it is, just as some people say you should try do what you love and to find your vocation ("Finding your vocation"), you should try live your life in such a way that you find that you are not deceiving yourself, i.e. your true self. As someone once told me, it is about as being honest and 'always being true to yourself'. If we are able to achieve this, then our lives too will be in synch with ourselves.