When the Doctor had cracked open door eleven, he did not see Daleks or Cybermen, disease or death. No. Instead he saw something he already knew but chose to forget. He saw the reason that made him continue to get more and more companions even though they always have tragic ends- the reason why he, even now, has to continue on these pointless adventures.

He saw himself alone. For he is always alone, even in company. For he is the last timelord and nothing will ever change that. He could be loved and adored by millions of people through millions of years, but that will not change that fact. So he just stared and whispered to himself, "Oh, of course," before closing the door once again. Then he walked away, like he always does to his own problems. He may be the Doctor, but even the Doctor can't fix himself.