Norepinephrine and adrenaline can cause a range of physical symptoms, like that flip-flopping feeling in your stomach. “Butterflies” might sound nice, sure — until they make you feel like you need to throw up. When you see, or even just think of, the person you love, you feel tense and nervous. Your heart begins to race, your palms sweat, and your face flushes. You might feel a little shaky. Your words might seem to tumble out of nowhere.