There's a great book, The Happiness Hypothesis by Jonathan Haidt, that covers a lot of this. From what I remember, experiments have been done that show your bod

There's a great book, The Happiness Hypothesis by Jonathan Haidt, that covers a lot of this. From what I remember, experiments have been done that show your body can react to stimuli before there is actual neurological activity, seeming to indicate that a lot of our rational thinking about reacting to things is an illusion, and is actually outside of our conscious control. We only justify our actions after the fact. I highly recommend the book; it was quite eye-opening to me when I read it.