You do not understand the heart is what God tells us in the Book of Prophecy (Ofudesaki). But what is this heart that God tells us that we do not understand? I do not believe that God is referring to the physical heart that keeps our bodies alive; but I believe it is the soul, which allows us to be conscious for eternity. Where is this soul in our bodies, and what is its function?
Some would say that the soul resides in the body, and others will say that the soul also can reside outside the body, perhaps in Heaven with God. Scientists have never located this soul, and cannot prove the physical existence. Perhaps the soul is comprised of only energy, like positive energy; and like a computer chip, it can store billions of information about our conscious mind?
God also tells us that the heart (soul) is like sand, which attracts our negative thoughts. The positive soul attracting negative energy, which coincides with scientific law that negative and positive energy attract. So the soul can be covered with the negative energies of our mind, and can be the storage center of our conscious. It is this soul with its baggage that leaves the body, when we physically die. Some would say that this soul would go to heaven or hell depending on how much baggage surrounds the soul. Those who believe in reincarnation will say that the soul will eventually inhabit a growing fetus, bringing with it the negative energy from its previous lives.
What happens to this negative energy that surrounds our souls? Physical law says that energy is never created or destroyed; it is only transferred. Perhaps, the negative energy causes cancer or tumors in our bodies; perhaps it is released from the soul, and comes back to us as misfortunes (accidents, natural disasters, etc.).
The last chapter (Chapter 17) of the Book of Prophecy, God again tells us that we still do not understand. We do no understand the pure heart (soul) that each of us inherently have. God tells us to sweep the heart of dust (negative energy). How do we do this? We must remove the thoughts of greed, arrogance, and self love. These are the negative energies that surround our once pure hearts. If these thoughts lessen, eventually our souls or hearts will be free of the negative energies. When this occurs, only joy will emanate from our pure hearts.