I think that maybe my heart uses your heartbeat as a metronome to stay on track. Yours balances mine, slows it, teaches it to beat strong and steady and with purpose and rhythm. When faced with the unfortunate but often unavoidable situation where it cannot hear yours, it forgets, simply forgets all it was taught. Like a piano student whose teacher skipped the recital. It aches for your sound to match. It stings for the audience of your lungs to hear it beat. Hear it sing. Hear it play.