This actually happened to me, and I think the first thing I ever publish for money will have some scene based on this included (whatever that is).
I was in Nashville, Tennessee for a conference back in 2002-2003 (I forget exactly). I was staying at a hotel about 2-3 miles from the strip. The strip, if you don't know, is a street in Nashville that pretty much only has bars on it, and the bars have live music playing pretty much every night (at least every weekend night), and even if you don't really like Country music you are pretty much bound to enjoy the experience.
I was walking back from the strip to my hotel room one night, a decently long walk, when I noticed me and this black man in his late 30s happened to be walking near next to each other. I said hi, he said hi, we started talking about where we just were and where we were going.
The man had just left his "woman's house" where he was going to comfort her because her husband had just died. He mentioned he didn't like her husband, but that he didn't want him to die. His wife wasn't there though, and he said that must have been "God's way of telling him he shouldn't see her today."
We walked on, him telling me about his life with this woman. Her first and third child were his, she said the second child wasn't, but he thought it was. She had first gotten pregnant when she was 17, her oldest child was now an adult.
He bought me a beer (I was underaged at the time), and we sat at the bus stop drinking, him watching for the cops, and telling me to hide the drink when they went by. His woman's husband didn't like him coming around the house, they got along ok sometimes, but I think the reason for their mutual distrust was fairly obvious. He kept on repeating though that she wasn't there and that must have been "God's way of telling him he shouldn't see her today."
His daughter was dating some guy he didn't like. He thought the girl should go to college, but she wasn't going to. He thought she was smart enough. She was working two jobs at the mall.
He would pepper the conversation with occasional side stories about some woman he met who was crazy in bed, or how he was picked up by some college kids and taken to bed by one of the girls, but it would always come back to how God was trying to tell him today was the wrong day to see his woman. She seemed to have lived across town, but he felt he had to walk back, instead of take the bus as he had gone.
His apartment was a bit before my hotel, but he didn't want to be alone, so we went back to my hotel and watched TV for a bit. When he left he was rather depressed about the idea we'd never talk to each other again (he gave me his number, which I lost).
The story, besides just being amazing, lends itself to a situation where the main character is wondering what "God is trying to tell him." I assume it could either work with City of God, or my as of yet unnamed novel. The fictional end I imagine is having the main character ending up at the house of some girl who he wasn't sure he was in a relationship with. He rings the doorbell and she answers and lets him in. As he walks in the door he looks up at the sky.
As an aside, my car, which I had left with a friend at Pomona College (outside of LA), was stolen while I was in Nashville. They found it stripped about a week later. I rode with a tow-truck driver back to LA, whose pattern of conversation was roughly the same as the man I had met in Nashville, though not quite as strange. He would just interchange between talking about his ex-wife, who he obviously still loved, and some crazy girl he was fucking. Several years later I met a Trinidadian-American in Prague, who again talked primarily about the girl he just broke up with (and some other exs), and getting laid (though more the goal of getting laid than the remembrance). I found out later in the night that he was actually a quite famous astrophysicist.