"Nurturing growth always follows two principles. One is: Stay out of it's way; you cannot "grow" another by will or technique. But the second is: Do not let it "overgrow" you. I have continually found that when parents can make the transition in their orientation from focusing on how to grow their children to how to prevent their children from overgrowing them, their children do begin to grow - that is, grow up - and so do the parents."
- Friedman, Failure of Nerve, pg 144.
In other words, the parent has to enforce responsible boundaries in his own life (not letting the kids run you ragged or drive you to distraction), before he can help the child mature into such responsibility, too.
This is also really helpful in considering "schools" of parenting. The unschooling homeschooler does great with principle one above, but tends to forget the second one. The strict and deliberate parent does fine with #2 but often violates #1. Maintaining both is the key.