I found for myself that these discussions forced me to think through what made sense to me and what I did and didn't believe. I realized that DS was astute enough that he could tell when I was bluffing. And when you are scared, realizing that your parent is bluffing is a scary thing. KWIM?
So part of the process is actually to figure out what makes sense to you and your understanding of the world. You don't have to know the answers, but be comfortable with something even if it is just accepting mystery. Once that is figured out, you can help your child much better.
