I blogged a few days back about reading and "the wet test," saying I read plenty of erotica that wouldn't necessarily make me come. I've been thinking about how this idea applies to writing.
There's plenty to say on this subject, but one point I'd make is that it's difficult to write erotica about subjects that really get me off. If just saying the words "nipple clamps" makes me want to come, I can grossly misjudge how hot my scenes are. When I'm blinded by lust, it's easy to go too fast. It's easy to imagine that what's going on in the reader's head is as vivid as what's going on in mine.
Some of my best scenes, on the other hand, have been about things that don't have so much inherent turn-on for me. My head is clear enough to pay attention to craft. I never submit a story until I'm turned on by the sex in it, but I think my writing is sometimes better when I have to work for it. There's a foreplay analogy in there, I think.
That said, hottest of all is when I can closely describe a sex act that really, really turns me on. But these stories are the hardest for me to write.