I think the hardest thing was, here I was and I should have spent a lot of time learning some real parenting skills, and a lot of other things, and all I had done was be a robot. I had a half grown family and was, as you too felt, a total novice. I felt stupid, and rather bankrupt of ability to handle child and teen issues I didn't really understand. I had to begin from scratch and all the books just didn't work.
My kids and I have discussed this alot. I have had to appologize way too many times. One thing I came to understand deeply is the importance of grandparents in a child's life and parents in mine. My mother had passed away, but George's mom was a real saint. We became very close after a few rough years. She just hung in with me, for their sake.
I did find that some situations were negotiable, others had to do with, well, "It's my house, I payed for it and you just can't demolish it or us for that matter". It did seem like a war zone at times. I think this is where I really began to look at my personal faith and made some strong decisions to for their sake.