Silences are as eloquent as words, and like words, they can act both positively and negatively. Sometimes our inability to speak is due to God's inspiration: silence,or a different way of speaking, would be His will, rather than what we were going to say.
Saint Porphyrios said : " If you can't speak to your child about God, speak to God about your child. "
Sometimes we cannot speak because the child reacts negatively, closing up, or even resisiting verbally, or leaving the room or .... In such cases the above word of Saint Porphyrios is relevant.
Conversations with Children, Communicating the Faith, Sister Magdalen