A/N: I love to imagine how 11 & 12 would think of Rose, and thus this story came into being. I own nothing.
After he left Rose on that beach the Doctor spent a great deal of his free time in what had been her room. He would pick up a shirt she had left on the floor and wonder if she ever thought of that shirt. Sometimes he would fall asleep in her bed, the sheets did still smell of her. He always woke up before Martha, so he never had to explain to her what he had been doing in a room that wasn't his.
With Donna it hadn't been so much of a secret; his relationship with Rose. He always felt like she understood what he was feeling. Donna would gently ask him about Rose, simple questions like what her favorite book was, or how they would spend their evenings. He never realized it, but Donna was trying to make sure that Rose stayed very much alive inside of him.
Even after he had regenerated and picked up Amy, he would still wander into Rose's room. It was something neither Martha nor Donna had ever seen. They hadn't spent too much time wandering the TARDIS, so they had never come across it. Amy had been much more curious and had discovered Rose's room within a few weeks.
One night the Doctor went to Rose's room and he found her in there. She was sitting at Rose's vanity looking through Rose's journal. She started when she heard him enter and tried to quickly hide what she had been doing. He shook his head sadly and took the journal from her.
"I've read it about a thousand times. I never tire of hearing what she thought of me and our adventures," he said sadly. She looked at her raggedy man and for a moment had no idea what to say.
"Doctor, who's room was this?" Amy asked timidly. He sat down on the edge of Rose's bed, his fingers tracing over the pattern on the bedspread. He had long since memorized what it looked like, but he couldn't help stare at it.
"Rose Tyler, she saved me from myself when I didn't even know I needed saving." Amy sat and looked at him, then looked around the room again. Her eyes came to rest on a picture of Rose and the Doctor, Rose's Doctor. They had their arms around each other and were smiling.
At some point Amy left him alone, but he didn't remember her leaving. He thumbed through Rose's diary and eventually fell asleep in her bed. The sheets were starting to smell less and less like her.
Eventually the Doctor hardly went into her room. He kept her journal tucked safely into his jacket pocket at all time, along with the picture of them, but he avoided her room. Foolishly he thought it would help him forget her. He thought maybe if he forgot her it would hurt less. But he never did forget her.
It wasn't until his next regeneration that he went back into her room again. He sat down on the edge of her bed, fingers tracing over the familiar pattern of her bedspread. The TARDIS had kept her room exactly as she had left it and had kept it free of dust for all of this time. All of the trinkets she had picked up from their travels were carefully arranged, along with some pictures of her and her mum.
"My dear Rose," he whispered as he laid back in her bed. "What would you think of me now?"
He fell asleep in her bed and dreamed of her. After that night he visited her room more frequently. Nothing could bring her back to him, but he could at least try to someone she would be proud of.