Though the tears had eventually stopped, Severus couldn't even muster the motivation to tell whoever it was to go away. It was likely Lily or Magius, or possibly Mr. Prept. Those were the only people here who would have cared enough to notice that he hadn't come down to breakfast. But he didn't want to see any of them. He didn't want to see anyone, ever again, to be honest.
It had been the same after Lily had died. If Dumbledore hadn't made him teach, he never would have gotten out of bed at all. But even then, he had done everything he could to save her, and he knew it. This time, there had been nothing he could have done. Once the earthquakes had stopped, he had been foolish to think that she would have been spared.
If he had known he would have lost her, would he have acted any differently? Would he have pulled away in order to protect his tender heart, or would he have spent every second talking to her that he possibly could, to have those memories, at least? He honestly didn't know, but it was pointless to speculate, because she was gone now, and all he had were those memories. And he would be glad to have them, someday, even if ... he wasn't, just now.