He knew it was coming. There is a room for everyone, he was everything but looking for this room, he was not scared, he was curious.
Then he felt it, like something pulling him towards that door, the 11th room, how ironic. His brilliant mind was everywhere at once. Maybe it was the daleks, maybe the cybermen. Maybe both.
Maybe it was Rassilon, maybe it was Gallifrey itself. Maybe it was The Master, or worse, maybe it was Koschei.
He opened the door and suddenly, just like Lucy Hayward said, he just knew it couldn't be anything else.
It was all of them. Not the people who sacrificed themselves like Harriet Jones or Jabe, or Astrid, but those other brilliant people, fantastic people who followed him, who traveled with him. People to stop him, people to keep him going. Like Donna said, oh Donna...
He saw her, and Rose, and Sarah Jane, and Ace, and Susan... and so many more. All of them lost. It couldn't have been nothing else but them, they weren't saying a thing; they stood there just looking at him. Their eyes saying "you gave us all, you took everything with you."
The last thing he could do was to not let anyone disturb this echo, even their echoes deserved more than to be disturbed by lost souls.
Then he felt it, the need to save Amy, after all his Tenth self went through, he couldn't loose one more.