It’s no brainer that whoever is reading this has been afraid at some point in the last minute, hour, day or week.  Fear is a constant gardener in our hearts and has cultivated plantations of our closely-guarded phobias. I don’t know what you are afraid of, we all have fears, we all have known fear, but I have made a strange observation; Fear, Love, Heartbreak—They are siblings in the same family tree.  
Whether I am nursing a fear, or blossoming in love or withering with heartbreak, my heart registers all these intense emotions as one. It’s in the quickening of the heartbeat, in the shortness of breath, the dryness in my throat; the symptoms are identical that I could substitute one emotion for another and my reaction wouldn’t vary that much.
They say love and hate are so much alike, but I beg to differ. My heart doesn’t thump in my chest when I meet someone I hate; rather it slows down and looks away in indifference. The people I hate are dead to me and I treat them accordingly.
With fear, or love or heartbreak, the heart flutters with anticipation, excitement, or pain?
What I think is that normally, we live in a nucleus of ourselves, comfortable in our own skin. With the addition of the above mentioned emotions, an imbalance within us occurs and demands we move out of this nucleus or seal the cracks that are making it unstable.  With fear, we strive to get away from this emotion and the imbalance it has caused. With love, we strive to encompass the new addition that would make this new super-nucleus complete (i.e.  a lover). With heartbreak, we strive to either reconstruct the super nucleus that includes our loved one or to reconstruct the singular nucleus that we had at the beginning before the pollution of a lover. This imbalance, I believe is what the heart reacts to and the reaction isn’t specific to a particular emotion.