A/N: Potential spoilers for River Song episodes. (Also, I don't own Doctor Who.)
She lives with constant pain, ever-present heartache. Gut-wrenching, heartbreaking misery.
Because of her Doctor. Her best friend, her husband, the love of her life. The person she loves the most in the entire universe causes her the most pain.
She has to hide more of who she is and how she feels each time she meets him, because she knows that every time they meet, he will know her less than he did before. And perhaps worse than him not knowing her is the fact that he does not trust her. Every time she meets him, his sideways glances become more suspicious; he is more hesitant to accept her help. She can't embrace him, or reminisce over their past, or tell him those three precious words that she always took for granted.
"I love you."
She can't tell him anything about their past—her past—because it's his future.
"When you meet me after this, I won't know you." He takes her tear-streaked face in his hands and wipes away a falling tear with his thumb. "And you have to be strong, because you can't tell me anything, River. And I'm sorry." He tenderly brushes a loose brown curl away from her face and tucks it behind her ear. A tear slides down his cheek and he closes his eyes, gently resting his forehead against hers. "I'm so, so sorry. But you can't."
For her, their happiest days are behind them. But that doesn't stop her from falling more and more in love with him every day.
Squeezing her eyes closed, she brusquely wipes the tears from her face and struggles to steady her breathing. After a long moment, she steps around the corner, forcing a smug, cocky smile. Because today, she gets to see him, and she will endure the heartache for him, her Doctor.
A/N: Yes, I know it's not confirmed that the Doctor and River get married at some point, but I like to think that it will happen eventually. :P
EDIT: Oh also, that italicized section is supposed to be a flashback from her past. I apologize if I didn't clarify that.