It was Christmas day a few years ago, and as usual, I was home alone. I don't celebrate the holiday and my housemate Lucy, a nurse, was picking up some well-paid overtime at work. It was mid-afternoon and I was on my third or fourth beer, lying on the couch watching TV and playing on my phone. The TV show was some average American sitcom about young single people, and of course, sex was mentioned a lot. I had been single...