I read something on the internet and it changed my entire life. I kinda wish I was kidding.
Anyhow- read it for yourself. It's from a much longer and more detailed/complicated website dedicated mostly to posture and the alignment of the human body. I'm fascinated by it from a massage therapist point-of-view, and now, also, from a "how have I been doing this wrong all these years??" point-of-view.
This is the same link, just easier to click. Enjoy!