Your heart is your moral center. It holds wisdom, judgement, discernment; it is the balance of ma'at, and if follows is perfectly true and will not lead you wrong. When I was first learning, I was told to "allow ma'at to ascend to its shrine" - to open my heart and permit it to connect with that ground of being so that I might be able to live in ma'at. The heart is a gift offered to the gods in certain rituals and artwork. Remember that the universal symbol for offering to the gods is ma'at - Her feather, a figure of Herself, Her essence. Your heart is therefore of one substance with Ma'at Herself.
The hieroglyph for the heart resembles a jar as much as it resembles a drawing of an actual heart. Consider what that vessel holds. It is the nature of a jar to contain things and to pour them out again.
Your heart unifies the members of your body. Each of your parts has a role in the system that is your physical form: your nose to receive air and life; your ears to receive wisdom; your eyes to observe and to hold your power; your belly to consume and assimilate, to carry impulses and urges; your hands to act; your feet to move. Each of these parts is important, but is not functional without unification with the rest of the body. That unification is achieved by your heart; your pulse can be felt in each of your parts, your blood reaches the most distant portions of your physicality. It is only when your heart becomes weary that you will die, your parts no longer connected by your blood vessels.
Likewise, your heart unifies you with the members of your community, with your family, your friends, the spirits, the gods: the wisdom and affection that you have for them brings you all together as members of a larger body. Your pulse is a part of the pulse of your family, of your community, of your nation, of your world; as you learn and listen to the patterns and rhythms of the cosmos you are reaching an understanding of the heartbeat of Creation.
Ma'at flows through all things.