Sometimes, it's better to let go of the past and learn from it. Something better could be waiting in his future. Just because a potential angel faded away does not mean his life is over. The real woman that he is looking for may be standing right in front of him, helping him whenever he needs it, being a true comrade to him, asking for assistance when she needs him.
Of course, they both fail to see this. However, as the audience, it is quite obvious. She was always alone, never really had a true family. Her flaws and imperfections made her so beautiful. She was a true Femme-Fatale, and fate brought her to this man. He was strong, but he was a little rough around the edges. He seemed careless, but he truly valued a woman's intuition.
He was not able to see that she started to see him differently. They became partners. He believed in her as much as she believed in him. They both, however, ignored their feelings.
It was never mentioned as much as the audience yearned for it. She never said what she wanted to say. She felt that she couldn't. There was no room for her in his life, she thought. There was never any room. He tried to brush away his feelings towards her because he was blinded by a woman of his past, a woman he could not let go of.
When he walked away, this was probably the first time she really felt like she was losing something special. Shots fired, but he trusted that she loved him enough not to bare his blood on her hands.
As he laid on the stares with his eyes closed, he finally realized what was truly waiting for him: the woman with the soft green eyes.