i think it is about believing that you are all alone, and no-one thinks quite the same way as you, and becoming withdrawn etc. but then one day realising that "you were there in front of me" and someone was there who understood and could be there for you. then seeing the world in all its colour, and not believing how it could never be like this before. then, "now that i know what im without, you cant just leave me here" because you dont want to go back into that black void, but become to rely on them to be the light for you.

thats how i take it, although that is pretty much repeating what others have said i think.