A.N: I was just watching The Silence In The Library and The Forest Of Dead and I don't know maybe it's because of the hour, I just have to write something.
Disclaimer: I've given up since the day they told me not to look for a Police box in the garden :(
Knowledge
''Everyone knows that everyone dies. And nobody knows it like the doctor. But I do think that all the skies in all the worlds might just turn dark, if he ever accepts it.''
River knew it better than all. Doctor's love for life. Perhaps she was the one who endured the most pain with him. But she knew, she'd endured nothing at all for him compared to all those legends.
No matter how knowledgeable or how trustable she was, she knew that she was no legend. She was the truth itself. The bittersweet truth that reminded him that everyday was no longer blessed.
He had lost his enthusiasm long ago. Even before the departure of Donna Noble, she realized. And as much as she could guess it had, even though the Time War, started with loosing Rose Tyler.
She knew she was no sun to his world. She was no true love. She wasn't the best friend he'd ever had, or the most experienced one whom he travelled with. She was nothing compared to all those Stuff of Legend.
She was his soul mate, his equal as mind no as IQ but as understanding.
She would never be as lovely and loveable as Rose Tyler, loyal as Martha Jones, she would never be the best friend like Donna Noble was once, she would never as suffer as, never be a hero as Jack Harkness.
But she didn't have to be. Because she also knew the Doctor loved everybody with both hearts, cared about anyone and everyone even it didn't matter to him anymore.
For River the choice was easy. She wasn't afraid of death and even if she'd died the Doctor would have find a way to bring her back.