Have YOU laid down Rules that your Son or Daughter have to stick to before they build their own Nest and leave home ?

We practiced for adulthood with them by gradually increasing responsibilities until they were able, at age eighteen, to leave home and be successful.

Your rules can only be applied whilst they are living in YOUR home.  You cannot inflict your rules, opinions etc. on them once they've flown the nest.  If you have taught them well and fairly they will probably do most things just the way you taught them but you cannot enforce it and, if you tried to do that, you'll probably find yourself a very unwelcome visitor when you call on them. They must experiment and find their own way to be independent. Advice is one thing, rules are quite another so I suggest you don't meddle.

If they're 18, they're not bound by your rules

Basic rules only: Have your own income, pay your own insurance for your own car and keep your room and bathroom clean. Contribute to the basic household needs but no, you are not my housekeeper.

We managed to live together for quite some time. It takes 2 to make it work and yes, that means respecting your grown childs' privacy and not snooping in their room and things. When her door was closed it meant "give me space" and we respected each other.

Now she moved out again into her own place and yes, I miss her dearly.

What are you babbling about?  Once your kids reach the age of majority, whatever that is where you live, there's nothing you can do at that point.

Every parent has laid down rules to their children who live in their house, regardless of age if they live in the house they follow the rules... or leave, pay their own way and make their own rules

Once they leave home their on their own.

hopefully i don't have a daughter , yet