posture

When I was young, Reader's Digest printed an article explaining how your sleeping position reveals your personality. Stuff like sleeping on your back meant you are secure and open in your life; sleeping on your stomach meant you are possessive and reserved.

But, now I'm older.
And my sleeping position doesn't reflect my personality as much as it reflects my circulation.  I'm finding that parts of my body fall asleep in different sleeping positions.

Poor circulation, right?
Good posture is supposed to aid circulation while you sit or stand.
So, I wonder, how do you achieve perfect posture while sleeping?
How?
If you sleep on your side, one shoulder must be shoved forward or backward no matter what kind of mattress you have.  I've never been able to balance on a bony shoulder.  Same thing with hips.  They have to be forward, backward or tipped toward your head.
Sleep on your stomach and your head has to be cranked to one side or the other.  And don't give me a pillow with a canal cut down the middle for my nose.  Unless that pillow is built into the mattress, you have to arch your back to put your head on it.

I'd be fine sleeping on my back, but my legs fall asleep.

Try this:
When you crawl into bed tonight, after you find a comfortable position, make like your mother just told you to stop slouching and sit up straight... only do it horizontally.  How does that work for you?

Anyone else ever considered what "good posture" is supposed to be when sleeping?