While leadership development has traditionally focused on sharpening the mind, far less attention has been paid to the heart, despite it being both the engine room of human performance and the seat of our capacity for connection, compassion, and courage. For senior in-house leaders operating under sustained pressure, the heart carries a dual burden: regulating physical stress while simultaneously holding the emotional weight of responsibility, uncertainty, and constant decision-making. This paper explores the heart from both a physiological and human perspective, drawing on science, leadership practice, and lived experience to make a simple case: how we lead is inseparable from how our heart is functioning.