Peter shook his head, as bewildered as any of them how he had come to that point in his life that betraying his friends, ensuring their deaths, was the only path that he could take. "I -- I don't know, Jamie. I wish I knew, I wish I had something to tell you about... everything."
He shrugged helplessly, hurriedly brushing away the tear that trailed down his cheek. He didn't have the right to cry, or if he did, it was in private, where nobody could see. "I've thought a lot about this, and I can't explain it. You lot -- you're my very best friends. There is nothing I wouldn't do for any of you."
He wanted to add that Sirius was full of shit. Passionate, angry, righteous shit, but shit nevertheless. No matter what had happened to cause this terrible chasm between Peter and his friends, the idea that Peter had never been their friend was utter shit. "I don't know why I broke my promise."