And there were so many great responses! Here are some of the top-voted answers:
1. "That their children are dickheads. 'Oh no, my James would never do something like that.' Well he did, and he's a prick."
"Worked at a summer camp, and absolutely can confirm this. I don’t care that you think little Timmy is an angel. He shoved another kid off the playground, and he’s a little shit."
2. "Spoiling your kid too much can leave them really unprepared for the real world."
"They can end up really useless or a complete asshole who genuinely thinks the world revolves around them. At some point, you need to teach them they aren't king/queen of the world, and they need to fend for themselves."
3. "That your children may turn out completely different to you — different interests, hobbies, ideologies, and religions."
"Don’t get pissy at your kid because he likes reading instead of football."
9. "You as a parent are responsible for teaching your kids proper manners and common decency. Not their teachers/tutors/babysitters."
"I briefly worked as a Japanese teacher, and I was surprised at how little some of these parents were involved in their kids' lives and expected me to address all their problems during the few hours I had them for the week."
17. And finally, "Above all else, YOU should be the safest person for your child."
"You should make it safe for them to be themselves. You should make it safe for them to have bad days or bad emotions. You should make it safe for them to exist. Because if you don't make it safe for them when they're a kid, it's really hard for them to find safety in themselves as an adult."
What's a hard truth that your parents had trouble accepting? Share your experience in the comments below!
Some responses have been edited for length and/or clarity.