River knew that the amount of time she spent thinking about her own death was unhealthy. But considering the number of times she and the Doctor had been in near-death situations, plus the fact that she had spent a fair few years locked in a storm cage for killing a man- well, it probably wasn't all that surprising really.
She remembered the first time she had met the Doctor. She had been a student then, on her first big dig, and he had come running across the site, waving his arms and yelling at them all to run. A few of her classmates had laughed at him, until they saw the storm that was following him. They had all raced to the underground shelter, making it and locking the door just in time. He had hugged her as soon as he saw her, rambling away about people she didn't know and places she had never visited.
She would never forget the look in his eyes when he realised that she had no idea who he was, and didn't recall ever meeting him. It was like a part of him had died. He had calmly sat her down and explained that he was a time traveller, and he would meet her at various points throughout her life, but in the wrong order. He had given her the blue book, telling her to write in it every time they met, and to never let him read it, or tell him anything about himself that he didn't know in his timeline. But his mood was like he was at the funeral of a close friend; she had half expected him to break down and cry at any moment. And he didn't seem to want to go either; it was a cross between not wanting to leave her side and being unable to be around her.
At the time of course it had made no sense at all, in fact he seemed a little crazy. Now it made perfect sense, and it scared her. The look, the pain, the distress, what it must have done to him when she said she didn't know him, it would all haunt her forever. In his timeline it hadn't happened yet, so she daren't bring it up to apologise for it, in case she gave away spoilers. And because he was getting younger as she was getting older, it meant that she would never know what happened to him after he had left the dig site.
The Doctor wouldn't tell her about the first time he had met her. "Spoilers!" he said, always with a hint of irony in his voice. She got the impression that he used the term because she had used it at him when he first met her, when of course for her it was the other way around. He was always quiet for a bit after she mentioned it too, which made her wonder even more about what had happened, or rather what would happen, on the day he didn't recognise her any more.
She now understood the pain in his eyes when she had told him she didn't know him, and knew she had that to look forward to. She knew that when she looked into his eyes and didn't see the spark of knowing, the memories of the times they had shared, and the love of the heart that beat for her (he had once said he had two hearts because he had two women in his life; one was River and the other was his 'dependable Sexy', which she assumed was the TARDIS) it would destroy her. Metaphorically and literally.
There would only be one reason she would stop seeing the Doctor, and therefore only one reason he would stop recognising her. So she knew that the day he looked at her and didn't know her would be the day she died. And that made a sort of sense. More than half of the times she had seen the Doctor her life had been placed in some sort of danger, it came with the territory. One day she wouldn't be able to get out of the situation they found themselves in, and she would give her life, probably to save his, and possibly numerous others too. Or at least that's how she hoped she would go. Surviving what she had survived only to die being hit by a hover car… well, it didn't seem right.
She sat and watched as this man who had once known everything about her and her future knew her less and less, and waited for the day when it was her turn to feel the crushing pain that he had felt years ago at the dig site. The pain that would destroy her.
Yes, the day her Doctor didn't recognise her any more would be the day River would die. If only because, to her, a life where she wouldn't see him again would not be worth living.
The first time the Doctor had met River Song he had seen her die. Looking back on the memory was like watching it through somebody else's eyes, which was partly because it had been a different set of eyes, and that wasn't the point. No, the point was that in his timeline she had already died, so there was nothing he could do to stop it without blowing a tiny little hole in space-time, which would create a vortex with an ion flux capacity that would swallow up the universe in the time it takes you to say the word "pop". Funny word, pop, one of those words that actually sound like the thing that you're talking about.
Anyway, yes, River. There was no way he could save her because, technically, she was already dead. He just wished there was and continued looking, just in case. Because she was special. He didn't know why yet, but she was special. He was starting to trust her, just like she had said he would, but he didn't know why or how she knew his name. And for the Doctor, not knowing things was frustrating, like new shoes, because however good the new shoes are, you always miss the old ones, because they were good too. Of course they were good, that's why you had them.
River was sexy too. Not sexy like his dependable old girl, a different type of sexy, but still a good sort of sexy. And she was sort of dependable too, but dependable for different things, like shooting things and knowing things and saying things and, well, sexy things. River things.
She wouldn't tell him about the first time she had met him. Too many spoilers. She had once said he was too young to know. Him, too young! She was the one who was too young. And her hair was too fluffy.
Normally he looked forward to meeting people for the first time, because they were always more impressed by things the first time they met him. Impressed, or scared. Sometimes both. But he wasn't looking forward to River meeting him for the first time. It was all backwards, and the first time she met him would be the last time he met her, like it had been the first time he met her. Or something like that.
Anyway, he didn't want her to not know him, because that would mean he would lose her. He had lost a lot of people, and he never looked forward to it (well, nearly never, some people are just annoying) but he was especially not looking forward to losing her. She had become something to him that he didn't know the word for. He supposed it was because she was dependable and sexy, the two things that made the TARDIS special, and imagining being without the TARDIS is like trying to imagine what life would be like if you were a boiled sweet.
When River wasn't around anymore he would miss her. A lot. He missed a lot of people, but he would miss her more. She would be more to him than a name on the list of people who had died for him, because she was special. His life went on, and would continue on for a long time to come, he had seen the beginning and the end of the universe and a thousand things in between.
Sometimes though, he wondered about when he would die for the last time. He had a feeling that River knew. The way she looked at him sometimes. He wondered if it was for her like it was for him; the first time she had met him he had died. It would explain a lot. And it was somehow reassuring. He wasn't scared to die, he had died before, it was a bit boring. But for his final death, he wanted River with him. Her gun and her smile and her too-fluffy hair. If only because if she was there for that, he would never have to be without her again.