I believe the self is known always by the heart, hidden like a treasure in our souls, and if one searches hard and deep enough that this light of knowledge of oneself from the heart can be achieved but only up to the maximum understanding. I do not think that it is possible to understand, moreover to know one's self to the fullest extent, as we are made up of very complex matter. I believe that we all go through many periods in our life when we are interested in finding out the precious secrets of the heart, and you come upon many times when you do really feel your heart responding to this urge or need. And just when you feel like you can reach out and touch this understanding with your finger tips, after long and strenuous periods of searching, this well desired truth of one's self all crumbles in the palm of your hand as a new truth is defined in the heart. This is because our lives and what affect it, is always in constant flux, so who we are and what we want to become is reinvented by these forces periodically as we grow. The soul unfolds itself like a flower with countless petals.
The knowledge of the heart about ourselves is however exercised through us as physical beings, i.e. our passions or cravings or misery's etc. For example a person who loves chocolate will hardly ever resist an offer of it, or when you here a certain song that you like, it makes you smile or become excited. So you do know what makes you happy or what fulfills certain desires but you may not know why most of the time, it may be because that song reminds you of something deep in the past that you have totally forgotten about, but this is an example of the secrets that are stored deep within. So you act according to what you think you are, without really being able to express this nature of self in words. .
