Premarital sex - I think the True Love Waits rhetoric is partly misguided and partly a good idea for protecting teenage girls from experiencing sex that will border on abusive, even if the teenage boy isn't intending it to be. I just don't think young men have the physiology to be empathetic lovers until they're a little older, and this can end up scarring young women. Sexuality gets more equal as people age. Virginity is a good thing and not something to feel embarassed about, no matter how old you are - but not being one is also not something to feel embarassed about. There is media pressure for women to be hyper-sexual and that doesn't take female brain chemistry into account; we are wired for monogamy and sexual safety, unless we've been abused, which is usually what causes the "promiscuity" that women get shamed & judged for. (Every neuroses is a manifestation of internal suffering.)
Getting married so you can have sex, which the Christian rhetoric sometimes leads to, is extremely foolish and dangerous, legally and financially and emotionally. Bottom line, it's nobody's business what is going on between two full grown adults (and there shouldn't be loads of shame and guilt attached), what "lines" they are nearing or have crossed, *unless* there is abuse happening, in which case there should be close friends who sexuality is safe to speak of with. Unfortunately, this will rarely be found in connection with conservative faith. I also believe it's possible and admirable for two people to marry as virgins. Is this grey enough? Ha!
Virginity is not Being Perfect. It does not make you better than anyone else. It does not mean your marriage is going to run more smoothly than someone else's, or that your bond is going to be stronger because you saved your psyche to imprint on your One And Only. I don't like the rhetoric Christians adopt around the upheld ideals. It's constructed from anxiety and a need to prove God and the Bible as absolutely true. (I can conceive of God and the Bible as true in a deeper, archetypal way that isn't dependent on the traditional stances being backed by scientific or psychological evidence. But that's something else.)
I'd much rather have my kids date and sexually experiment as adults before/while finding their eventual spouse than go through what I did. Young marriage is not the smartest trend in our day and age (although many can make it). I'm going to encourage my kids not to marry until they're 24/25 or older, which has good statistical backing. If they choose my cultural tastes (which they are free not to, and won't scare the hell out of me if they don't), that will probably mean they'll do something sexually before then (which will be none of my business and I won't ask about), because they will most likely fall in love before then, and will have healthy biological systems that will make them want to act on the love. This is not the end of the world, although hopefully they can manage to do it without getting pregnant or getting a disease.
That's the main health that I *do* see in traditional sexual ethics - protection against abuse, pregnancy before a relationship is ready for it, and sexual disease. Monogamous sexuality is going to protect you the best from extra suffering, and all the world religions had this in mind when developing their guidelines. But a surprise baby or an STD does not make you Satan! And a surprise baby can be incorporated into your life without rushing into marriage, which is another not so great idea Christians tend to deal with things with.
Love happens. Sexuality is connected, and that's a good thing. Don't hate yourself for anything, all will be well in the end, it's hard being human. At the same time, be smart and don't screw around with nature, because you are just as likely to get a disease or "fall pregnant" as the next person. And if you want to save yourself for marriage, that's admirable and attainable! But God is not going to reward you for it. Do it for the peace of mind, emptiness of womb, and health of your privates.
That's my take. The end. :-)