In 1998 movie Sliding Doors, a London woman's love life and career both hinge, unknown to her, on whether or not she catches a train. We see it both ways, in parallel.

Washington - It was 2008. Barack Obama had just been elected president, and I was full enough of hope to try an earnest men-seeking-men post on Craigslist.

Josh replied. "I like your pictures and I'm interested," he wrote. He made up a lewd joke. I laughed. And we met.

What I remember most about our first meetup was his dog, Rudy. It was the first dog I met that responded to Spanish. Both Josh and Rudy liked that I knew a little.

Over the next few years, I learned a lot from Josh. The short version is that before I met him, I knew how to have sex and after I met him I knew how to cuddle. I'd often fall asleep on his chest; his heartbeat was such a lullaby. 

He was the first boyfriend to whom I introduced my roommates. I would walk from my apartment in Greenwich Village to his in the East Village practicing "I love you." But I don't think I ever said it to him. Lots of "I love this" or "I love the way you _____." The closest I got was learning karaoke in Spanish for him.

Our relationship ended without an ending. The time between dates just grew longer and longer.

"We had a special thing," he texted me recently from France, after I sent him an old photo I found. "You were sooo sweet. You were brainy, chipper, and spunky. You had an infectious smile and a gentle touch. You were always somewhat nervous, but you were tender and sincere. Your words always seemed poetic to me, quiet and still. Maybe it was the still of the night(s). I think we both left imprints on each other's heart."

And then he wrote: "Had I sensed you were willing to settle, we would probably be married by now. Why didn't we?"

But here was a wedding question I had never considered: Why didn't we?

I'm 38 and single. Never been asked. Never done the asking. I've seen a lot of marriages: rebounders, high school sweethearts, college sweethearts, office romances, cautious and considered courtships, ticking biological clocks, power mergers, green-card marriages and impulsive trips to city hall.

My texting with Josh flirted in that playground of possibility that, inexplicably, our relationship never entered. What if I had stayed a missionary in China? What if I had attended another college? Moved to another city? Nailed that job interview? Learned another language? Tried sporting a mustache?

There's a "Sliding Doors" quality to wondering about past relationships. That movie wasn't about regret or serendipity, but rather the question: What of our essence transcends our circumstance?

Why didn't we? It's a question that dares you to consider how you've thought through problems in your life, and how your thinking about marriage might have changed.

A straight friend, Teddy, said that when an ex-girlfriend asked why they never got married, he couldn't bear to tell her the truth - that he had gotten bored sexually - but he was amazed at all the assumptions in the question. Why is marriage the obvious endgame? Why would getting married years ago presume they'd still be married?

When people ask one another "Why didn't we get married?" the subtext implies that they approve of how you've turned out. There's a bit of wishing, after the race, that you had bet on the winning horse. In 2008, a nobody named Adele made her US debut at the 184-seat Joe's Pub in New York; what inane nothingness was I up to that night instead?

Before I could think seriously about marriage, I had to love. The first time I knew I was in love, really in love, was with Dave. He was the first guy I ever considered marrying, the first with whom I went so far as to envision our lives together. We were 25. It was a disaster of a relationship.

I think about Josh and Dave sometimes. And Jason, Cy, Tal, Ron, Javi. Everyone has their list.

Some sliding doors are locked. They're memory cul-de-sacs, roads to nowhere. But others seem open-ended, as though there's still terrain left to explore.