I'd amend this to say "Dating as an adult," since I believe that teenagers should date, if only to get an idea of how NOT ready they are for marriage. However, I don't believe in anything more than casual dating when you're under 18. You're simply not old enough/mature enough to make a life-long decision at that point.
Even the person you trusted most with your life can let you down. Some people view commitments and families as disposable items. You can't change them. And you'll find they aren't worth your effort or time or loyalty. Empty narcissistic wasband.