Is It Ever Okay To Make A Relationship Ultimatum?

Boy and girl or boy or girl and girl or several of each meet and like each other and everything's all smiley and hunky dory until you bulldoze your way head-on into a big unmovable. What to do?

I don't mean to Carrie Bradshaw out on you; lord knows it's Sunday and I'm sure TBS is playing watered-down reruns of Sex And The City if you want your fix of Elementary Date Lessons involving copious amounts of consumerism. As a seasoned veteran of many a failed relationship, I've been thinking back lately to the times that one person has demanded something of the other- explicitly demanded- and am trying to decide whether or not that's ever acceptable. On one hand, people can't expect to control the person with whom they're romantically involved, but, on the other, sometimes a breakdown in communication occurs and the only way to express your disdain for a behavior is to call for it to cease if the relationship will continue. Sometimes you don't know that those behaviors exist until you're already neck deep in things.

I haven't demanded much of people that I've dated, but when I have, I've always retroactively questioned whether or not I've been in the right. Was it okay for me to tell that boyfriend who taught at a college that I wanted him to tell his starry-eyed former student that it was inappropriate for her to text him at all hours of the night, even though he thought she was just a harmless child? Was it okay for one boyfriend to demand that I stop responding to emails from a former fling who lived halfway across the country? Is it okay for a wife to demand her husband stop spending time with his best friend, a woman he's been close with for ten years? How about a partner demanding that his partner not go to dinner with an ex boyfriend who's only in town for the weekend?

These things seem like they should be common sense if you're the one making the demands, but often seem irrational and out of line if something's being demanded of you. If you're the collateral damage of a relationship ultimatum- like, let's say, for example, that your ex boyfriend's new girlfriend informs him that he can no longer talk to you, even though neither of you have any residual sexual desire for one another- it can feel like two forms of betrayal, and it fucking hurts.

Relationships are not easy or simple unless you're dating a real doll or one of those really disturbing sex teddy bears that I wish I had never found out about. They're filled with mystery and strange bodily smells and the taste of another person's spit and learning where someone keeps his towels and what his thoughts are re: leftovers and whether they should be tossed or saved. When things get complicated, when your partner starts asking things of you, how much should you bend? How much can you ask from them? Is it ever okay to say "do this, or it's over"?