I hate you.
That tore my heart out... which makes it a good story! You drew me into the characters and made me feel what they felt.
The characters were real. Their reactions were believable and relatable. The thing that I would review about them though is some of the soldier's verbal responses. "Deserving of your company", for example, isn't something most people would say out loud. :)
There were a few grammatical errors, but... well, of course, I would notice that, right?
Anywho, it was good. :) You're very talented!

Reviewing as I read.

"Ya know?" is a bit too informal for something outside of dialogue unless the story is being told in first person.

When David first speaks to the woman as she's trying to open the door, "giggle" should be "jiggle."

Anything following dialogue, such as "he said", should be separated by a comma instead of a period. Example: "I didn't know that," John said. Or if it's an exclamation: "I didn't know that!" he laughed.

I like the way Sarah tries to find something in common with him by starting a smoking habit. It's very true how people will go out of their way and do things they really don't want to just to find something to talk about or a reason to see someone every day. It's very realistic. And I like the friendship they have at the beginning and the humor you add to their exchange and Sarah's excuse for her coughing and choking on the smoke.

That would be such a heartbreaking letter to read! I would lose my mind if I read that last sentence!

Good job! Realistic dialogue. Short, but didn't contain any unnecessary information. I would, however, like a little more insight to the characters' looks. It would be nice to know what the beautiful woman who caught David's eye looked like.