They were both liars. Both killers. There was the blood of good people on their hands, people they cared about and it was never coming off. They knew the real heroes were dead. The only difference between them was that she kept her promises whereas he never made any.
Miranda never should have asked him to "stay safe". 'I spent two years bringing you back'. There were no second chances now. No time to rest and the way they said each other's name was exhausted and desperate.
Hell they never should have started 'this'. She was smarter than that. Her instincts told her "no", to push everyone away, even Oriana, especially Oriana, and then there was Shepard. He made her accept that she was human. They were both drowning in anger, naivety, and loss, but when darkness was all you saw you just had to close your eyes. She taught him that. John should have known she was just trying to comfort him. She never believed in herself, in anything she said, but she believed in him. She wanted him to keep going when no one else could. He made her stupid. He made her laugh. He would probably get her killed and still she wanted to thank him. With him she had truly lived.