To know that no matter what, their parents will be there to help them, take care of them, protect them, give them food and shelter, and emotional/physical love
as far as I can tell, the main difference between people who are completely overwhelmed with parenting and those who are having a great time raising their kids is that the latter don't really consider it a big deal when their children are upset with a decision they made
One thing adults conceal about sex they also conceal about drugs: that it can cause great pleasure. That's what makes sex and drugs so dangerous. The desire for them can cloud one's judgement—which is especially frightening when the judgement being clouded is the already wretched judgement of a teenage kid.