Disclaimer: Doctor Who isn't mine... yet.
He could pinpoint the day, or rather night, it had all started, but he could not imagine the day he would not want it anymore.
The night it had started, had been a time for a rare nap, when she had suddenly shaken him awake, whispered his name over and over in a strangled, panicked voice. He had pulled her down to the bed, held her tight as she calmed down enough to finally tell him about the horrible nightmare about demons telling her she was going to die. She fell asleep in his arms that night and he smiled as he dozed off with her.
After that night, their nights together became more and more frequent, and he did not complain. He looked at his beautiful companion with a smile on his lips. Her head was resting on his chest, one hand grabbing his shirt, as though she was holding him in place, making sure he did not leave. Not that he would. He had never liked standing still, but having her with him like this, definitely made it worth it.
Those nights, he would stay awake and watch her. He would push away stray locks of blonde hair and tell her stories about his life. About Gallifrey, the Master, Susan, Ian, Barbara, Sarah Jane, Adric, Tegan and all the other people, who had passed through in his life.
And in his ancient, melodic language, he would tell her how very much he loved her. How he would burn up entire suns to stay with her. How his hearts started beating faster whenever she was near. How her beauty blinded him.
He fell more and more in love with her on nights like these. These nights, when he never felt alone and all he could do was staring at her, enjoying her closeness.
And when she was gone, he missed her the most at nights. And to a pillow, which smelt like strawberries, like her blonde hair, he would repeat how much he loved her. He would still say beautiful she was in his dreams. He would say, how he would never forget her, and he would gladly burn up another sun to get her back.
He wished he could have spent an eternity of nights with Rose Tyler.