When I was a brand-new writer, I wrote a few erotic short stories. (I’m not talking about second grade! I’m referring to many months ago.) This was a strange choice, given that I later went on to write science fiction short stories and a middle-grade novel about spy kitties. But as a writing exercise, I recommend it. (And just for your sake, I will admit it.)
If you’re just getting into writing, write until you make yourself blush. Write until you cringe. If sex isn’t your thing, describe something so gross, so fetid, so ripely putrescent you gag*. (Then go back and take out all the adverbs. Then try it without the adjectives.)
Sex scenes are hard, and horror has a narrow market, but they both tap into your emotional stronghold. You can’t get there without letting down some barriers. You can’t do it well without smashing those barriers flat. Behind them, you will find the right side of your brain (as opposed to the left side of your brain). (CAUTION: I’m speaking as a writer, not a doctor, otherwise there would be a slew of medical references here instead of a parenthetical comment.) The right side of your brain is a great place to write from. The left side will tell you, “Oh, Heather, you can’t write THAT, your MOTHER might read it!”
So my advice, culled from the advice of many many greater writers: Unless you are writing a Mother’s Day Card, don’t worry about your mother.
P.S. This is obviously not a post about HOW to write a sex scene, but if you’re looking for that, check out this WriteWorld post on tumblr
*Paraphrased from a friend, quoting one of his writing instructors. The original quote involved something about lepers and pus.