Love unrequited? That love is desired in return - this is the implication - yet it be not.
Why do I sound like yoda?
Like Joa said, if your heart aches for someone, to be loved by someone; if you aren't complete without them / you would die without them - this is obsessive stalker material. (ie. people who request block checkers)
True love isn't about receiving - it's about giving. It's about letting someone know you care without needing anything in return, and wanting to give someone more love than they could ever love you.
I used to tell my fiancee that I wished I could be her guardian angel, so I could watch over her. I would protect her from any harm and make sure that she would have everything she wanted. Everything would be perfect. She would never have to worry..
..she would always know she is loved. And yet she would never know how much.
*sniff*
Okay, I've just reread that and it sounds soppy to the point that bender's gaydar would explode. Let's never talk of this again.