fractured pieces

When do you let someone or something go?  when do you say im finished with this?  more importantly, how?  how do you detach your soul from someone else's? its bound to be a messy process.  any time you let someone get to know you, really know you, you end up giving a little piece of yourself away.  and that's usually fine.  good even.  we need others to know us and understand us and we need to know them.  

but what about when you want that piece of you back?  when you need to just let the person slide from your life and you dont want them to take that piece with them? the things people say, like "everything happens for a reason" or "maybe it's just time" do nothing to soothe a hurting soul or restore the missing piece.  what does?  I have no idea.  

I just know i dont know how to let go, or when to say there is nothing here for me anymore and walk away.  because even when i think i have 'let it go' and moved on or past it or whatever, something happens, or is said, or i see a glance across a room and suddenly its just there.  the connectedness i thought i had severed.  there, real, and FRESH.  and im back where i started with no idea how i got there or what I am supposed to do now.  There ought to be step by step instructions for this kind of thing.....