People assume they will teach their kids lots of things. Then they move on to knowing they don't need to teach, just help/assist/facilitate. But there's that other area where the kids know things we don't know (and maybe could use knowing). By the time you get to that stage, confidence is easy to have, I think.
"Something has clicked, or melted away, actually, in the past year and I just wanted to thank you. Thank you for saving my relationship with my children. I feel happiness and lightness where there was once dread."
"Don't shelter them from the world. Don't let them loose in it. Walk with them, paying attention to what it looks like they need to know (not what you think they should know). Partner with them in this real world we live in, so that they can learn, with your guidance and support, how to make the most of their explorations and their ever-growing experience."