His dreams were all that he could live for. In his dreams she was there. She was always there. Her touch, her voice, her eyes, her love; they were all there. His dreams were all he had left.
Outside of those dreams it was dark, so very dark and he couldn't breathe without her gentle touch to his cheek, his hand. All that got him through the waking hours was her presence. A silvery depiction of her that hardly did her justice always following him, hovering an inch away from him; spurring him on through his day, encouraging him to make some sort of effort in his now so empty life.
And it had worked, for a time. Seeing her, and being with her in his dreams and having some semblance of what she once was in his waking hours. But not anymore, he couldn't do it anymore. He'd waited too long, he needed her. Without her there was no life. He had no life, and he couldn't breathe. He couldn't breathe. He needed to find her, he needed to find his soul but he couldn't because she was gone. Gone.
And Severus couldn't breathe, because Lily wasn't there anymore.