The Doctor was like a star, a brightly-burning star that held a solar system in place. Everything revolved around the Doctor, because he was the last of his kind, and his kind saw time, and controlled time, and yet were outside of time. He could see all timelines, fixed and manipulatable, just by looking at a planet, or a galaxy, or a single event, and he used himself to keep time running smoothly, to stop the universes from collapsing or sinking into a dark reality. The Doctor was the sun of the universe, but sometimes he wished he wasn't. He wished he didn't have to carry on with the burdens he held, and he wished that he wasn't so hot and dangerous and explosive that every single person he got close to, every person he cared for and took with him got burned in the end. He wished he didn't destroy everything he got near for too long, he wished that his chosen name was more true. He wanted nothing more than to able to fix what he broke, heal what he hurt, keep what he found, but he always, always, lost everything. And now he'd lost something in a way that hurt him more deeply than anything had in so, so many years.
"Rose." It was barely a whisper, a thought carried away on a shallow breath, but it was the sound that carried all of the pain and loneliness and grief on it, away from him and yet back through him again in an endless wave of hurt and loss. "Rose!" It was a cry this time, torn from him on a sob and a yell, and written in the tears that poured down his face. This was emotion like he hadn't felt since the Time War, since he'd lost everything, and it was emotion he'd thought he would never feel again, but it was back. It was the feeling of having the things that mattered most torn away in a single instant, of losing it all in one blow, of losing first his family and now his Rose. It couldn't be described as mere loneliness, or grief, or loss, it couldn't be put into words, but it hurt more than anything, it hurt to be alive. It hurt to move and to breath and to think, and it hurt as his hearts beat in his chest, because it hurt to know that Rose was gone, as gone as his family and his people, only worse, because Rose was still alive, just trapped away from him. It hurt to think about how he'd almost got to keep her, and that it was his fault she was gone, because it was his fault that lever wasn't secure and so it was his own fault that he'd lost another person. The pain didn't make sense, he wasn't hurt physically, yet it was there, so clear, so defined. It felt physical, and again he thought of losing his family and how it had felt.
The Doctor was in so much pain it hurt to move, it hurt to do anything but look at the white wall that seemed as if it should be hiding Rose and yet was not, the wall that was so blank and simple it required no thought to look at. His head rested against the wall and tears streamed down his face, and it was all he could do to keep from crumpling to the ground and curling into a ball, but he was stronger than that, strong enough to turn and walk back into the TARDIS and carry on. He was a star, and stars kept going until the very last second, until their supernova burned out and left a black hole that consumed all that was before it. He couldn't afford to become a black hole; he would consume the universe, destroy it all. He had to carry on, even as his hearts broke and he was shattered. Just as a star began to decay as its core filled with heaviness, the Doctor came closer and closer to destruction with every painful blow his life thrust upon him. He was a star that was shattering slowly, was already shattered part of the way, and he knew that when he hit the breaking point the universe would be in danger. He was a shattered star, but until he became a burning supernova, he couldn't allow himself to be a black hole. He had to carry on with all his cracks and his broken hearts until he was split beyond repair, until he couldn't anymore, he had to keep the black hole at bay until he couldn't any longer, because the Doctor was the sun of the entire universe, and the being the sun was more important than his brokenness.
This is a little one-shot I thought of while watching "The Next Doctor" and "Planet of the Dead" while I saw the Doctor changing more and more as he lost more and more people in different ways. Since I love Rose so much, I used the scene near the end of "Doomsday" to show how I think he feels.