As to the meaning of the
VNV Nation song.
I've listened to this song ALOT and I think I've come to appreciate it's meaning, which is very deep and emotional. I think what Ronan Harris is talking about is his personal journey through life (consisting of deep contemplation, etc.) and his realizations about human nature, and how he has "come so far, that I cannot return" and that "nothing I can do that I have not done." He feels that he has reached a crux of realizations, and he cannot make any further progress towards 'enlightenment' (or whatever you would like to call the goal of our journey to understanding). He "cannot hear the words by which (he) guides".
He is faced with all these conflicting realizations and ideas that he cannot reconcile, and a dearth of general philosophical ideas that are tearing him apart. Thus, he is faced with a lack of guide, and a constant feeling that he's been here before.
That's the best I can explain it in words. I think I've had a similar crisis as the one expounded in this song, and I can really feel Ronan's pain and anguish here. It's a rocky road for those who choose to reconcile philosophies and find the truth within, but it's not an entirely lonely existence.