Sweden has been elected the happiest country, the bestest country, the best country for working women, etc. Less than 15 percent of our population considers religion to be a significant part of their lives. (See, I can even spell "their", though English is my second language.) I don't know anyone that goes to church/mosque/synagogue/temple/etc regularly. In Sweden, it's accepted to live together indefinitely, whether you're married or not, so the ones living together are usually happy together. Divorces, for married couples who want to split up, is usually a fairly easy affair; you split what you have in two, share custody of children if you have any, the one with whom the kids are going to live most keep the house and compensate the other, if the kids live more with one than the other, the other compensate the first for expenses for kids. (If you're not married and have lived together, and want to split up, either party take what they brought into the home, and the custody process is basically the same as for married couples.)
Sex is something you have because you want to, not because society or others expect you to. Parents know that teenagers will have sex, but teenage pregnancy is almost unheard of, as contraceptives are free for teenagers. Contraceptives for adults are affordable and easily accessible. If the worse comes to worst, abortion is available at all women's clinics and major hospitals, at the same prices as any other medical procedure (i.e. around 30 dollars). Up to week 16, the woman decides for herself, week 17-21 there needs to be a medical reason for the abortion. After week 21, it's considered a premature birth and no abortions/forced births are allowed except to save the woman's life/health, or the life/health of the fetus. Not having to worry about unwanted pregnancies is bound to lead to more relaxed and probably happier sex-lives.
Here's my slogan: Relax and have fun, be inclusive and open-minded, and sex will be a natural part of your life.
I'd say mine would sell better...