***, have you ever had a serious relationship?
I even do not know what to tell you, ***

You operate with terms like "serious relationship", let start with it. I do not understand that strange combination of words. What do you mean? just try to describe it, using your own words.
I always think that relationship has the only important quality: they should bring pleasure and good mood. Does having fun brings you pleasure? Are you happy when you are joking, when you are smiling? When you are having sex? Are you happy, when you dance with a girl, when you flirt, when you play? I hardly could imagine a link between relationship and "seriousness". What is
seriousness? In what place it should be applied, and what for? Is is that about wife brain-fucking her husband, or vice versa? about blames, mutual jealousy, scandals, questions like "where does that hair on your shirt came from?!", dull and stupid reproofs, shadowing and offences? Look, ***, you can met all that perfect ******** exactly among those people who consider themselves to have "serious relationship".
The foundation of so called "serious relationship" is lie and self-deception. in a burst of love people tell each other a lot of false words, vow fidelity, tell that they do not need no one else, and sometimes start to believe in all that stuff for a certain perioud of time. But all that farfetched "serioussness" and faithfulness remains a soap bubble, and only a matter of time/case helps to reveal it.
It all could be compared with the laws of the market. Different companies offer you different conditions, this one has got a better price, that one has good quality, third one has another advantage, and so on. And you make your choice. This is a competition. The same is in relations between people! An attempt to create some unique monopoly (serious relationship) is just a weak attempt to fence yourself from the rest of the market (other people) and to enjoy a privilege of this position. It might work under some conditions, for example if one marries an ugly wife, who is not wanted by anyone. But if a girl is sexy, and if she is not frigid, during most of her life she will have a lot of propositions, and again, it is only matter of case if she will agree with one of them. She might say no once, twice, keeping in mind all that "serioussness" and her self-invented moral liabilities, but what for? if the variant is good? This is one of the things that is completely wrong in "serious relationship". Cuz she (or he) does accumulate all that cases when she said "no" and refuse to other man. And during that accumulation, the amount of anger and reproofs to her partner increase, till one day it will blow out in a scandal like "what the fuck I ****** my life with you asshole, blah blah blah". Or, understanding that possibility, she start to met someone secretly.
of course, you can be an idealist, and see everything through rose-coloured spectacles, but in real life all that "serious" bullshit usually means a lie, mutual lie or lie from one of the partners.
So, I ask - what the heck is that simulation needed for? Why can't everybody acknowledge a right of your partner to do what they wanna do? if you girl have a "serious realtionship" with you, and she see a sexy man whom she want to fuck - she will need to apply every effort to keep faithfulness. But this is *****, nothing good is in restricting her. Her desire is more impotant, since it had appeared.
I think that only voluntariness is the right foundation of relationship. Not a *****! nothing good comes with *****, no matter who is restricting you - yourself, of you jealous partner. Thats why only open relationship are really durable and solid. Cuz every second I am with my girl I can be sure: if she is with me, she wants it. There are some reasons for it. And that reasons are in her free will, nothing is holding her except her desire. Not a bullshit like marriage, not a bullshit like moral obligations, not an awareness of serioussness or responsibility (another stupid word, that has nothing to deal with relationship)! Only desire, interest, inclination and attraction are the real things, the fair things, the real clue, the real foundation! and if a girlfriend has that attraction for me, I do not give fuck with who else she would like to be.