I think "ghost" refers to someone you can' t get. Kind of like the idiom "give up the ghost." He knows he can't get her, so she's a ghost. And he says "to know that you're almost mine" shows how close he was to getting her, but in the end she is just a ghost, and he has to give up. I think with all the references to the dancefloor, he might have met a girl and took her dancing, or met her out at a club, and they hit it off, but it never worked out.
I think "ghost" refers to someone you can' t get. Kind of like the idiom "give up the ghost." He knows he can't get her, so she's a ghost. And he says "to know that you're almost mine" shows how close he was to getting her, but in the end she is just a ghost, and he has to give up. I think with all the references to the dancefloor, he might have met a girl and took her dancing, or met her out at a club, and they hit it off, but it never worked out.