The heart is a funny thing.
Scientifically, it is an organ that pumps blood through you and jeeps you alive. Its rate speeds up when more energy, or blood is needed. It doesn't mean anything.
To us, it is the center thing in our core that holds all our feelings. Our deepest secrets. Our fears and insecurities. Our heart speeds up when nervous or in love. Our heart blooms when we find new feeling. Our heart keeps us alive in more than one way, but the main way is it keeps us feeling.