when is enough, enough?

"no girl should ever forget: that she doesn’t need anyone who doesn’t need her back".
-Marilyn Monroe

There's a space in my heart that I have yet to fill, funny thing is I am positive that I've typed this before.  I understand, you cant control who you love; so of course you cant control when to stop loving someone.  Problem is: how do you continue to love someone who doesnt love you?  Better yet, when do you stop loving someone when you've had enough?  I guess if you've actually had enough the feelings or love would stop on its on....... 

I have no clue, obviously.  I just want to stop *wipes away the tears*