My guess is that the narrator is either supposed to represent a friend, family member or a soldier, etc.
The begining of the lyrics is sort of like an exceptance of the narrator's fate, and thanking someone for the life they've known, or the adventures they've had with them -
"Thank you, I'll say goodbye soon"
Telling them their eventual death isn't their fault -
"Though it's the end of the world,
don't blame yourself now."
And the classic 'I will always be with you' thing, though I admit I'm not sure about the part that fallows -
"I will surround you
and give life to a world that's our own."
And as it goes on "I'll say goodbye soon" turns into -
"I'll say goodbye now"
And near the end it all gets dissoriented and muddled as the narrator
slowly fades away and dies