As far as i know, Narator only describe our feeling ... so we feel like we loose something that we can never get back ...
That may indeed be part of our self ... or something simmilar, that we loose, bcs we are changing.
OR!
And i think i dont need to say that i find this option more probable, but i just did anyway. 
It can be something spiritual ... or simply collorfull description of remorse ... we know that power is "unclean" ... and yet we used it, we were "pure" before and we lost that purity, forever, with no way to get it back ... like remaining scar on our soul that will never trully heal.
