I guess the author's intention is to express that each person have both sides, the inner you is always hidder and what you behave is not really following the heart.
This is a very common and interesting phenomenon of social psychology. As each individual is socially wired to others in our socail groups, what we do and how we react are always attached with a series of consideration or let's say boundry conditions. In may cases, this is not our real thoughts but we have to do it like this way. The real personality is always hidden behind us and complete freedom is our pursuit of life.