I've had shyte posture and it's true your body mirrors your brain.
The flipside is changing your posture also helps the way you feel.
Read up, or better still do an evening class in yoga, pilates and particularly the Alexander technique.
The bonus is you always get a few Babes on these things and quite often dancers (my fave). Then ask them to describe how they feel when they are doing it.
I do martial arts as well and my posture was still terrible until I did the Alexander technique, it's very much about body awarness and I'd recomend it to anyone.
There is also research that shows people subconsciously age you by your posture and gait as well as the way you look. For oldies like me they think I'm 20
, well thirty something maybe.