No, not your own sex life. I hope that's already healthy. I mean sex in general and, in particular, your teenager's sex life. They may not have one yet (are you sure?), but they will sooner or later. And you want to make sure that when they do, it's happy and safe and fulfilling, not furtive.
What is the single factor most likely to give your teenager a good experience? And, indeed, the confidence to delay that first experience until they're ready? That's right: Being comfortable with the subject. The more your child knows about sex and finds it easy to talk about, the more able they will be to say no, or to insist on a condom, or to respect their partner's feelings.
You can pretty much take it as read that the more you talk about sex (and drugs, alcohol, smoking, and all the rest) at home, the more confident your teenager will be in making mature decisions for themselves when the time comes. Even broad-minded parents who report strong relationships with their teenagers generally say that this is the trickiest subject to discuss comfortably, probably not least because teenagers also report that they find it difficult. But the onus is on you to show that it's a perfectlyacceptable, normal thing to talk about.
School will teach your child the mechanics of sex, of course, and very probably also the basics of HIV and STDs and how to put on a condom. But your kids will giggle their way through this with their friends, and it won't tell them anything about the fact that sex is a normal part of adult life, and that it has a complex relationship with the emotions. You'll have to tell them that -- don't count on school to do it.