“This was inspired by the 2nd episode of Justice League Unlimited, and a Superman comic book, both entitled “For the Man Who Has Everything”:
 
Info on the comic
 
“Again, this one is open to interpretation, and here is my interpretation; Celestia is trapped in a dream that is giving her everything she ever wanted in her life. In order to leave this dream and return to the “real” Equestria, she must sacrifice her heart’s desire, and give up everything good she ever wanted in her life. (which is pretty much what happens in the comic, and in the Justice League Unlimited episode)”
 
Boy, what I wouldn’t give for a MLP adaption of For The Man Who Has Everything.