Parenting advice?

What is some advice you've heard from people who don't have children? It makes me laugh when people who aren't parents try to give me parenting advice. Not saying I know it all, but don't tell me kids should be sleeping through the night if you don't have any. Or that I should be able to "control" my child's emotions. Or that when you have kids they will not misbehave in public. I tend to just laugh and say ok, because everyone who doesn't have kids is the perfect parent. What's your best piece of advice you've been given?