It's sad when you actually thought you've gotten over someone, and you're doing really fine with your life, but then that someone comes back and you feel that pain over and over again. Only, much painful.

And yes, it's sadder when instead of walking away so you wont have to struggle again, you'll just ignore the sane part of you that tells what's the right thing to do and draw yourself closer to that person making yourself once more vulnerable to the point that no matter how much pain that person inflicts you, you just cant let go.