Why do we grieve for people who don't deserve it?

Why do we grieve for people who mistreated us, who abused us, who continue to hurt us and harass us? Why does it still hurt, when all you wanted was freedom the whole time, and now that you have it, all you want is to go back, and yet at the same time, the thought of it disgusts you?

How can we hate a person with all your heart, and at the same time, still long for the way he cared, the way he kissed you on the forehead, and the feeling of security and affection that came along with him?

Yesterday, I wrote the meanest thing I've ever written in my life to a person who I at one point I was head over heels for. 

I'd like to say I regret it, but I don't. I'm not going to apologize. I'm not going to respond any more to his taunts. 

It felt good for a little while. I felt empowered, like a badass, I guess. But that feeling's gone now, and all I am left with is grief. 

Grief for a person who treated me like sh*t, and still continues to six months later, and still proves himself to be worse of a person every time I hear from him. 

I feel anger. Burning anger, like a hollow in my chest, that seems to radiate out of me. I haven't felt anger like this in so long, it almost feels foreign to me.

I feel cheated, like I devoted this much time and affection to this person. He was such a big piece of my story, and he's just gone without ever giving me a proper goodbye. Not only that, but he enjoys taunting me.

I feel sad because he's really led his own life down a horrible path. I knew that he was broken when I met him. I wish that I could have fixed him while we were together. But I couldn't fix him, because I still needed to fix me too. But it's the thought that I could have helped him, I would have helped him, I just wasn't in the right place.

I wish I could have helped him. 

But I didn't.

And that, of all things, hurts me more than anything.