Hindsight
If you're honest with yourself, you saw this coming. The exact moment of realization isn't something you can really pin down. It probably happened so gradually that the exercise would be futile anyway, but you know that in the coming weeks, months, and god forbid years that you are without her it'll be something you'll obsess over, because that's what you do.
You did it with Laura, your college girlfriend who ditched you for one of your so-called best friends who didn't even feign guilt when he dragged her around to dinners and parties, shoving her into the face of anyone who –willing or not- would acknowledge his prowess with women, and his ownership of her. Sometimes you speculate when it was that the first girl you ever really loved let her gaze wander to that guy over your shoulder, that guy who wasn't anywhere near as smart or engaged or sincere as you in anything important or worthwhile, especially her. It was so long ago, and you've loved so much harder, but every time you bungle your latest relationship you always think of Laura, and wonder.
The haircut. It isn't what started it, probably isn't even in the same galaxy of concerns that caused Donna to pick her head up out of the sand, -or, well, stacks of paperwork you continually hefted on her -and get the bright idea that she wanted something better than you. But it signaled something, a loss of her bambi-esque outlook and the ushering in of a new era of growing cynical reservation. She gave up on you, and you don't know why.
When you asked her to spy on Toby, when you convinced her we should spend 50 billion dollars on a mars landing because some pretty NASA scientist bat her eyelashes at you, when you started trusting someone a decade younger than her to start advising you on "presidential stuff," when she had to stand in the oval office and calmly tell the President that there were parents in the mural room begging for their son's life, when she saw Charlie graduate, or when she sat and watched an intern argue over base closings while she was only there to take notes.
So many different events, all seemingly unrelated, except that you know Donatella Moss better than the constitutional line of succession. You know that somewhere along the line, during any one or all of those moments she paused. She paused and took a step back while simultaneously taking twenty steps forward- because she's oh, so good at that- and asked a single question: "When will it be me?"
You don't know when it started, but you know it started somewhere, and as much as it kills you to think of filling her cubicle with someone else's clutter, with someone else's smiles and disapproving frowns and laughter, you know she's right. She deserves better. You've always known she did. You just can't figure when she realized it too.