Carrying purses

Most people hunch their shoulders forward and upward to keep a purse "in place." If your purse is very heavy, you do need to use your traps and pecs to prevent your shoulder from being pulled excessively. But you don't need to overcompensate and hunch. Only use the muscles to the point that they maintain a neutral architecture around your shoulder joint. Most often a purse is not very heavy and you can use it to gently stretch your traps and pecs and improve your shoulder positioning. Place the purse close to your spine (unless you need to watch out for pickpockets), use your elbow to nudge the strap or purse toward the spine if the length of your strap allows that, and let the weight of the purse gently stretch your shoulder back and down. 

How about golf clubs if you want a challenge?  I try to keep the bag behind me (rather than to the side) and let it pull my shoulders back. If I get my other arm behind me and over the bottom of the bag, I feel like I am in decent posture. It's not easy because the terrain is usually up and down and guys like me tend to put their heads forward while walking. My 'oh-so-slow' improvement in posture has allowed me to play more than a couple of days in a row and I have high hopes to better that.

I'm learning from reading your post - thanks!