Damn, I wrote some rude shit. Sorry, I was pretty buzzed during that and I don't even think I read it properly. But these are things I've thought about and I can give an answer.
Really what I ended up concluding is that people need constructs to function, and people have varying levels of flexibility with these depending on how badly they need something to be the case. So like in one of the cases you brought up, "what a relationship should be"—well some people will have very rigid ideas of it, like thinking a woman should have dinner ready by the time the guy gets home. Other people will be more loose and think that they can develop that idea with their partner. Both are still constructs, but one is more fluid than the other.
Another thing about constructs is that you have one of your own about all of these things. You have to have some conception of what friendship is, you have to have some conception of what a relationship should be. And again, these probably vary in flexibility. The good thing about people having constructs is that it makes them straightforward to work with. Once you know how they think about certain things, you know what buttons you can press and which ones you can't. So constructs are good for this reason.
There can be a point where you almost have no construct about the things you brought up, and that's when things become more nebulous. It's impossible to not have thoughts about relationships or friendship, but it is possible to reach a point where the rules either basically don't exist, or generally don't matter. If you find yourself in that space, just remember to be a nice person.
