Fight-or-Flight response. I tend to experience that quite a bit. Having a sensitive stomach it becomes apparent fairly quickly for me. What I realize is that when I am tempted I experience this. My stomach becomes really weak all of a sudden ("Inhibition of stomach and intestinal action") and my heart rate rises ("Acceleration of heart and lung action").
This is an epiphany to me but at the same time I've known it all along. It's God's Spirit working in me to produce holiness, to lead me to holiness. Fear, leading to a Fight-or-Flight response.
Oh, and Fight-or-Flight response shows itself by inhibiting erection.