today this guy was talking about how you don't necessarily have to feel an emotion before you do the behavior associated with it. sometimes if you just do the behavior, you'll start to feel the emotion. for example, people generally think they need a reason to laugh. they think they need to something to make them feel joyful first. but if you just start laughing for no reason, at first it is forced but very quickly it devolves into real laughter and when you are all done you feel a bit joyful. i find it works with smiling, too. (and probably some negative emotions as well.)
anyway, the point of this is that my first thought about this phenomenon was that it is an interesting glitch in our psychology that it can work essentially backwards. i'm not saying we shouldn't exploit it for all it's worth, it has some great applications. but i think it's an interesting way for things to be set up and i wonder whether it is something that was selected for or if it just happens to be an interesting side effect of how our emotions and behaviors are connected.