When I meet a client for the first time I ask them to stand up straight, whatever that means to them. Then I ask the first of many questions—are your shoulders on top of your hips, behind the hips, or in front of the hips. There is the rare being who claims to be perfectly upright but  most everyone else says that their shoulders are in front of their hips.
When I tell them that their shoulders are behind their hips they don’t want to believe me. I have been through this scenario with so many client and while it amuses me in its consistency, it boggles my mind that no one knows where the body is in space.
To learn to stand up straight is a matter of perception and our openness to change. It can be easy to change but not many people embrace the concept. I find pain to be the greatest incentive for change but everyone really needs to address the way they perceive themselves in space or why they perceive themselves incorrectly.
I have a theory for why this happens. We don’t care about our shoulders, we only care about our head and where it sits. We think we are standing up straight if our head feels right. When people stand up in front of me in their idea of straight everything tends to be out of whack except for the head, which sits relatively level upon the top of the spine. When I put someone in my image of standing up straight, the head usually goes haywire falling forward in space, which is admittedly uncomfortable and even off putting.
If a client has a good amount of core tone I can show them how to correct the head in a reasonable way but if we lack the strength in the core necessary to hold up the spine, it can be very difficult to successfully bring the head to its proper alignment.
To keep the head in its proper alignment and stand up straight underneath it you need to align your bones properly and develop the necessary core tone.
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