Why do you miss someone when they could be bad for you, or you bad for them?

It's odd, I was speaking to someone today, and a whole shedload of memories came back...my fondness for them, how close we were at one stage and so on. It was great chatting (although it was very brief and we didn't really say too much if I was honest)....and it was always nice to know she was ok.

But it struck me...and hard...I miss her in my life.

It's mad, even after all these years I really miss her so much, even though she doesn't work or live too far away (just a bus journey)...thing is I know that even if we were to get together (which to be honest is highly unlikely) it would not be a good idea as I don't honestly think I would be good for her, or her good for me.

Why does life do this to me?