Better to have loved then to have never loved at all.
It's a horrible thing, APD. I've experienced it a few times, although, I've never experienced it truely, because we somehow patch things up in the end. But the memories are still there.
Being in love, or similar with a great friend. You feel if it is a rough day, you can go see them, and you know things will be okay. They will support you, love ya, what have you. They were there for you, committed. Then... they're gone. And doing the same thing for someone else.