Thanks for posting this question. I read it a couple days ago and had to read it in context, mull it over, read it again, and mull some more 🙂
I think reading further down in Section III helped me:
“The problem before the educator is to give the child control over his own nature, to enable him to hold himself in hand as much in regard to the traits we call good, as to those we call evil:––many a man makes shipwreck on the rock of what he grew up to think his characteristic virtue––his open-handedness, for instance.”
Perhaps the application is actually fairly simple. We need to be intentional as parents in training our children’s hearts and therefore the words and actions that come out of those hearts. We do our children a disservice if we don’t prepare them for making choices to live out good and avoid evil. It is not enough to tell them what is good and what is evil. It is a daily training of hearts and minds (ours and our children!) to see our strengths and weaknesses, to allow God to work in us to convict us of the evil that lurks in our hearts, and to help our children recognize the prompting of God to do good and the strength He gives to do it. (Yes, I realized that’s reading into this short passage a bit).
I’m still very much in learning stages myself here, but in our house, I think of the way we train our children about truthfulness. We don’t let our oldest be the perpetual confessor, or our next child be the sneaky one, which appear to be their natural bents. We train them all in speaking truth, confessing when we have not valued the truth, and we use consequences that reflect the painful reality that where there is not truth speaking, there is not full trust. I think in this example, our children learn from a young age that truth telling is just the easier way to go, and so, while we are always revisiting this habit and depending on God’s grace when we fail, generally our children don’t have to think too hard about whether to tell the truth or not. They’ve learned from experience that life is just easier, more peaceful, and more satisfying when they tell the truth. One less decision to sap their processing powers at any given moment 😉