Why does your heart beat very fast when you did something wrong?

Your heartbeat speeds up and your palms sweat for no apparent reason because of the sympathetic nervous system. This system kicks into action when you perceive a threat or feel anxious about something, and it responds by increasing your heart rate and sending more blood to your muscles. However, modern living can trigger this response even in the absence of actual threats, as when we feel embarrassed, stressed, or guilty.