I am very interested in better posture in part after coming across the work of Dr. Paul Ekman (http://www.paulekman.com/), a pioneer in studying facial expressions and emotion. While the conventional understanding is that you feel an emotion and only afterwards does your face express that emotion, Ekman asserts that it is a two-way relationship. By assembling a facial expression you can trigger the associated emotions.
Elsewhere I have read similar descriptions of emotions being strongly influenced by your body posture overall, not just your facial expressions.
So if the habitual arrangement of our bodies affects the likelihood of feeling positive or negative emotions, then posture probably deserves a role in our attempts to be physically and psychologically healthier.
