He was lying in a pool of his own blood thinking how long it would take him to die. All alone, alone again, alone in life, alone in death. How fitting. One minute? Perhaps a whole hour? Probably not, judging by how hard it was becoming to breathe, despite him trying as best as he could to close the wound with his hands. They were shaking and he didn't do a very good job of it. Why he tried, he didn't know, there was nothing for him there.
Only it wasn't true. There was one woman he could be persuaded to stay for, but that could never be, as Severus knew she would never care for him, how could she? And admitting his defeat, he finally let go and his hands thudded to the floor.
It was a matter of minutes now. He would soon die and everything would be better for it, it was only right. It was what he deserved. He wished it wasn't so, but when did him wishing something actually changed anything?
His last thoughts were of her and, dying, he, with all his heart and magic, wished her such a happy life, that the feeling hurt him, he wished that she would smile and love and be excited every minute of it and thought that if there was something, anything he could do to make sure it happened, he would.
And so strong was his wish, that it kept him alive a minute longer and then one more, it kept him alive cocooned in the magic of a dying man' last selfless act right until the moment she finally got to his side, crying and frantically throwing healing spells on him and making him drink all the nasty potions all the while telling him that he just can't go and taking his hand and kissing his knuckles and begging him to stay with her.
Little did he know that she would never be happy without him.
And so he stayed.
And then two wishes came true.