Okay, I just had a brainwave.
I think the song is about how everyone grows up wanting to be someone else, a big movie star or a rock star or something. How they think they'll make something really big out of their lives, but eventually their dreams are shattered.
"All the stars watch over you, night and day, when you can't stop turning". It means that while your life goes on, you have your own personal dreams and beliefs, which you will try and get as close to as possible, and all the while the heavens will constantly watch over you.
"Where'd you go, mysterious? So ashamed, you've lost the way again". I reckon the song is written from a parent's perspective, and this part is referring to when the kid has grown up a bit and the dreams are already shattered. Where did the mystery of your goals and dreams go? When did you decide to just let happen what will come to you? When did you decide to be just a normal person? The parent is ashamed that they didn't support you more ALONG THE WAY to accomplishing your dreams, so you've lost the way and gone off on a tangent.
"When did we all start living the world in a photograph?" It means that since when did kids start looking at magazines and movies and think: "one day, I'll be that big". Everyone just went about with their daily jobs and never really had many dreams pre-1900, or so I've heard.
"... where I'll find you waiting for something." You're waiting to be seen and recognized.
"When [your] dreams are done, look how the tears run, through MY eyes". It would be much more emotional for a parent to realize that their child has given up on a dream, and has just accepted that they'll be a standard nobody. Or it could mean that the child would want to take out his emotions on his mum or someone close to him. Run and cry, I mean. "Oh I'll never become as big as those singers and actors".
"You danced upon the mirror glass, on the floor, when the sky was falling." Perhaps a bit melodramatic. You danced around with your goals and dreams which came from "mirror glass" (maybe a TV or computer screen, where you see all this celebrity bullsh*t), trying to accomplish them and be something, while the "sky was falling", or, the world was turning without you noticing. Everyone else abandoned the concept ages ago and are getting on with their lives, but you're still wasting your time trying to become a somebody. As for "on the floor", it means that you're still very small, and it's adults controlling the world (eg. their heads are in the sky, another word for the top of the world, which they're bringing down with their actions; "the sky was falling". This might refer to the more powerful figures in society).
"Where'd you go, my curious? Insecure, you've lost the way again". Could just a rewording of the previous sub-stanza, but the "insecure" refers to the kid finding out that their dreams are shattered, and are off the "way" to becoming someone big.
The next stanza refers to the kid being a bit more mature now.
"What once went through my head, once was in my head". It means that the dreams are all just memories now, and all you can do is remember your ecstatic fantasies.
"Through my eyes". You can still see the celebrities, but that's all. You watch them, but you don't have motivation to become one of them any more.
WOW THATS A LONG DEFINITION
