(If instinct wants to sleep with someone but reason doesn't, it is preferable for me to not sleep with them. This probably doesn't sound like a surprising conclusion, but I was confused for a long time.)

Actually, I'm not surprised that someone could take a while to figure that out-- there's what I call the romantic fallacy (romantic in the philosophical sense, though it happens to overlap with common usage this time) that people's unthought impulses are sacred.

To put it mildly, what (if anything) is sacred about people is a complicated question.