this song is about the vision of Spike when he was under the effects of the door which brings to the worst nightmare, and this is what he felt in that moment. Or at least as I think xD

LYRICS: 

we have lived very well together
but everything has an end
remember when you said "our love will last forever"?
I'm not like you, so you send me away

and I regret (if I made you sad)
you won't forgive (and I understand) 
your spot of sight,
leave me if you want
but please

Don't forget me
walk your way and
smile when you remember those times, and please
don't surrender
nor give up and
smile when you think of me
(when you think of me)

and now I am alone, on my own
the only hope which lights my existance, your happiness

I don't deserve (the time you spent with me)
I want to mend (the pain you have inside)
I love you so
if you're happy, my life's complete
but please

Don't forget me
walk your way and
smile when you remember those times, and please
don't surrender
nor give up and
smile when you think of me
(when you think of me)