I'm 40, the cute girl from upstairs is 23. When she stopped by to commiserate about loud neighbors, we had a beer, went dancing, and then had sex. Afterward, she seemed weird and left abruptly. I wrote her a note, "Sorry if I made you uncomfortable, but I love you and look forward to seeing you again." She hasn't looked at me since. Where did I go wrong? -- Mr. NeighborGrateful as you may be to a girl for having sex with you, it's never a good idea to let on. You could've had a future with her -- the...