Because

When I told him that I was marrying her, he paled, and stared.

I remember telling him that I wouldn't ever leave him for someone else, and he believed me.

My parents didn't force me, and they wouldn't have needed to. I proposed to Pansy because it was the thing I felt I should do. I thought I'd feel happy, or upset. But I didn't feel anything, except remorse, because marrying her meant giving up him.

And I didn't love her.

Pansy was beautiful. But she was beautiful in a sort of nice way, totally the opposite of what the other Syltherin girls were. She was easy to read, easy to quiet, and easy to hurt.

But Harry...

He was beautiful, period. His messy black locks, his bronze toned skin, his dark emerald eyes...he had a mysterious air about him that Pansy lacked, an air that she never had. Harry's mere voice could set my body afire, I could near damn come just by the rough panting of his breathing next to my ear as he would talk to me in whispered words.

I married her, because it felt like it was something I was supposed to do. If I hadn't, Harry would most likely be dead, rotting in a ditch somewhere, and I wouldn't be there to save him.

When I told him I was marrying her, he paled, and stared.

I remember telling him that I wouldn't ever leave him for someone else, and he believed me.

My parents didn't force me, and they wouldn't have needed to. I proposed to Pansy because it was the thing I felt I should do. I thought I'd feel happy, or upset. But I didn't feel anything, except remorse, because marrying her meant giving up him.

And I didn't love her.

But I loved him. Harry believed I loved him. And I did.

I didn't leave Harry for some girl, some woman I could never love sexually. I didn't leave Harry, period.

I left Pansy for Harry.

I left Pansy, for Harry Potter, the boy who I loved.