I think I may have said this in another thread, but I told my young kids something along the lines of:
"You go to school and learn math, reading, writing, science, etc., but nobody there teaches you how to be a good husband or wife. Your mom and I are your teachers on that and honestly, we're doing an awful job teaching you the right way. Neither of us want you to think this is normal, especially if you get married someday and behave with your spouse the way we have. I think divorce will give each of us a chance to become better teachers someday."