Pray and then speak.

That’s what to do with your children. If you are constantly lecturing them, you’ll become tiresome and when they grow up they’ll feel a kind of oppression. Prefer prayer and speak to them through prayer. Speak to God and God will speak to their hearts. That is, you shouldn’t give guidance to your children with a voice that they hear with their ears. You may do this too, but above all you should speak to God about your children. Say, ‘Lord Jesus Christ, give Your light to my children. I entrust them to You. You gave them to me, but I am weak and unable to guide them, so, please, illuminate them.’ And God will speak to them and they will say to themselves, ‘Oh dear, I shouldn’t have upset Mummy by doing that!’ And with the grace of God this will come from their heart.” He also said, “It is not sufficient for the parents to be devout. They mustn’t oppress the children to make them good by force. We may repel our children from Christ when we pursue the things of our religion with egotism.

Elder Porphyrios in Wounded by Love quoted here.