Justamom, if a daughter, she can go on chaperoned dates beginning after grad school. Which is a little incentive for accelerated learning. If a son, well, we'll just take him over the border for a little seasoning at 14 or 15 if you know what I mean
Its that pesky double standard.
The best advice I have ever been given and I share with my friends (especially the starry eyed ones) is don't get have kids and don't get married. And I mean that in an unexpected way, don't be in such a hurry or make a mistake you pay for in the long run that will define your life for you. That way, most wounds do heal.
As far as what I would really say to him/her: Don't get married/pregnant, expect to feel hurt and do what are ready to do. But I could see myself adding for a daughter: You can always do it, but you can't undo it . . but that is the double standard again.
The rest of it won't be what you tell them it will be if you supplied enough of the elements that build self esteem, and they took from them and learned.