The speaker piles up labels for a person they love: future, past, present, world, everything. But the list keeps turning darker. This person is also "heartache," "heartbreak," a "disaster," a "nightmare." Then comes the twist: "You are me." The one being addressed seems to be the speaker's own flawed self, or at least someone so tangled up with them that the two can't be separated.
The mood is intense, restless, and a little bruised. The repeated "My" shows how completely the speaker feels bound to this person, while the contradictions show how painful that closeness is. The subtitle, "A happily Ever After Based On Lies," hints that the fairy tale isn't real.
The last two lines carry the point. Running from this person is really running from oneself, and until the speaker faces that, they stay a "shadow," present but not fully alive.