Rose went away, so the Doctor was blue. Ask Donna, "where's the Doctor?" she'll reply "Doctor Who?" Sarah Jane and Martha, and now both the Ponds, had their fun with the Doctor, but now they're all gone. So ask me again why the TARDIS is blue—there's a sad man inside with both his hearts torn in two.
Sometimes, if he is in the right mood—or wrong mood, as it were—the Doctor lets himself remember. He had lost so many, will lose so many more, had his hearts broken far too many times. He tries not to remember—it hurts too much. But there are times when he cannot help it.
Rose Tyler. The first person he was close to after he had done the unthinkable. His brave, brave pink and yellow human. At first an innocent shopgirl whose life he had both saved and ruined, who then came back, refusing to let his gruff exterior put her off. Someone who refused to give up on him, who had done the near impossible to return and save his life. Someone he had regenerated for. The first and last face his tenth body saw. The one that body had fallen absolutely and undeniably in love with. Someone he had cried for, when she was locked in that alternate dimension, shed just one tear, with all of his pain and love locked inside it. He had burnt up a sun just to get to say goodbye to his Rose. His clone, him, with all of his memories, but human, was left with Rose to ease her pain, but it could do nothing to ease his own. People loved Rose, the sweet blonde from London—even the Daleks. His Rose. The Bad Wolf.
Captain Jack Harkness. Flamboyant, bisexual, flirt, first a con man, then a hero. He had saved Rose in the London Blitz, and Rose had saved him on Satellite Five when the Daleks attacked, brought him back to life, made him unkillable. A former Time Agent who had redeemed himself and became a member of Torchwood, and also a friend, even as he drove the Doctor up a wall with his constant flirting. Originally a coward who had found his bravery. The Face of Boe.
Mickey Smith. He had originally tagged along for Rose's sake, against the Doctor's wishes. He had been there since the beginning, been captured by the Nestene Consciousness, and had chosen to leave the Doctor to protect a world not exactly his own from the Cybermen. The tin dog, once upon a time. But, much like the real tin dog, he had proven his worth, becoming a proper hero of whichever world he chose to protect. Mickey the Idiot, who had turned out not to be such an idiot after all.
Martha Jones. He had first met her in a hospital, the hospital that had been transported to the moon. She had been a young medical student, then become so much more, although she was not entirely wrong saying she was a sort of rebound from the loss of Rose. She had fallen in love with him, though, being his normal oblivious self, he hadn't noticed. He had been trapped by the Angels in 1969 with her. She had left him of her own free will, unusual for a companion. She had gone to join UNIT, to help save the world at the very end of his tenth body. She had married Mickey Smith, swapping the unattainable hero and time traveler for the one she could have. The Girl Who Walked the Earth.
Donna Noble. He had met her just after losing Rose, then met her again, properly, later. A companion so similar to his ninth incarnation, full of sass and fire and nerves of steel. A companion who never fell in love with him, who was more likely to snap at him than moon over him. She was older than those he usually took with him, but that made her no less a worthy companion. She had been saved in the Library. She altered much of history by doing no more than turning right instead of left. She had reunited the Doctor with his Rose, for however short a time. And it was largely thanks to her that his clone had grown, absorbing some of her characteristics, and giving her a part of the mind of a Time Lord. But that part of her mind was too strong for her to bear, and he had to wipe her memories, losing her forever. The Most Important Woman in the Universe.
Amy Pond. Little Amelia Pond, once upon a time, with her fairytale name. He had met her at the very beginning of his eleventh body, when he was brand new and still cooking, then had left her for five minutes…and come back twelve years later to find Amelia gone and Amy in her place, all red hair and legs and anger at him for abandoning her. She had called him her Raggedy Man, and her last words to him broke both his hearts. She was a fighter, always going all out for those she loved—him, her husband, her baby. The Scottish girl in an English village—and she kept the accent. She ran away with him on the night before her wedding. She had grown up with a crack in her wall, a crack in time itself, and so had powers of a sort beyond even his. She brought back Rory. She brought back her parents. She even brought back him. And then he had lost her to the touch of an angel. The Girl Who Waited.
Rory Williams. He had really come along for Amy, the girl he loved, and who, in her own odd way, loved him back. He had died, had never existed, had been plastic, had waited two thousand years to keep Amy safe. Had been a Roman, a plastic Roman. He had been a nurse, perhaps in a way to keep up with Amy's fantasies about the Doctor. Mr. Pond, because with him and Amy, that was how it worked. The Last Centurion.
River Song. Nice hair, clever, and good with a gun. Hell in high heels. Born Melody Pond, the children of his best friends, but stolen so, so young. Stolen and raised a perfect psychopath, raised to kill the Doctor. Had done so, more than once. Poisoned him in Berlin on the eve of war, just after she had regenerated. Shot him, against her will, on the shores of Lake Silencio in Utah. Didn't shoot him, and rewrote history entirely. The first time she had met him, in his timeline, she had died. He had held her as a baby, she had heard about him as a child, regenerated in front of him. The archaeologist, his wife. The time traveler. They met in the wrong order, back to front, her past as his future. His Bespoke Psychopath.
Clara Oswald. Born to save the Doctor. He had met her in the Dalek asylum, in Victorian London, in the twenty-first century. She traveled with him, in what she referred to as the snogbox. A nanny to two children, two little Daleks, Angie and Artie. She had entered his timestream in Trenzalore, split herself into echoes, let herself be everywhere in his history, all at once. She had died a million million deaths to protect him. The Impossible Girl.
The Doctor hated remembering, hated how much it made him hurt, but there was nothing he could do. He had to remember. Had to honor them. Honor their memories. To remember and mourn.
Everybody knows that everybody dies, but nobody knows it like the Doctor.