“I can’t live without you.”
It is only on a technicality that this sentence is any different from “if we break up I will kill myself.”
And to anyone basically sane, that sentiment isn’t romantic – it’s downright terrifying. Think about it. You might think you’re being sweet by telling your partner that they are the only thing that makes life worth living. And if things are good between you, they might even think it’s sweet, too. But what if things go sour? What if one of you really just doesn’t want to stay in the relationship anymore? Would you walk away from someone, however much you wanted to, if you genuinely thought you were the only thing that stood between them and suicide? I know I wouldn’t.
Being dumped sucks. But it sucks a lot less than someone staying with you purely because they think you’ll put a bullet in your skull if they walk away.
It is also entirely possible I am overthinking this in the extreme, and people who say “I can’t live without you” don’t literally mean “if we break up I will kill myself,” but I think that’s far too thin a line to be treading in the practising of healthy, mutually-consensual relationships. Just don’t do it. Please.
“I know you better than you know yourself.”
No. No you do not.
In every single situation I’ve been in where I have heard this (always from a man, funnily enough) it has never succeeded in doing anything other than getting my back up. The most recent person who said this to me was a so-called friend who insisted that I really, really wanted to sleep with him and was just in denial to myself, and routinely insisted that he knew exactly what was going on in my head before I even knew it myself. It didn’t take me very long to lose it, let me tell you.
It’s a very effective way to remove someone’s personal agency, it’s the height of arrogance, and it is NOT romantic.
You know what’s romantic, as well as just a decent way to behave? Accept that the expert on any individual’s personal experience is THEM. Listen to them and believe them when they tell you where they’re coming from. Do not say “no, what you really think/feel is this.”
There are two people in the world I sometimes feel can read my mind, and they are my beloved Nomad and my best friend J. And y’know what? They have known me intimately for years and as such have a very good picture of me and how I think and feel. But they don’t tell me what I feel, or tell me that I am wrong about my own experience. That’s a thing you shouldn’t do to anyone.
The expert on me is me. If that hurts your ego, you’re not mature enough to date me.
“You should JUST KNOW…
…what’s wrong/exactly what your partner wants in bed/if someone wants to have sex with you/if you’re serious or casual or exclusive.”
This trope is often spouted in glossy-magazine level relationship psychology bullshit, in which people are advised to passive-aggressively communicate with their partners through a mixture of body language, veiled hints, and leaving a magazine or romance novel open at a particular page on the coffee table.
And I can understand why. The idea of “just knowing” is a seductive method of trying to avoid the difficult, often complicated and sometimes messy business of actually communicating within a relationship. If something’s wrong, don’t get pissed at your partner for not knowing exactly what it is without being told. If there’s something you really want in your relationship but aren’t getting, however big or small, you cannot reasonably expect your partner to know without you actually telling them. However much you love each other, you’re not mind-readers.
Not to mention this trope is dangerous. If you’re supposed to just know when somebody wants to have sex or what they like in bed, and asking is seen as ruining the moment, then consent kinda flies out of the window, doesn’t it?
Be an adult. Use your words.
 Obvious exceptions apply. My ex appeared genuinely baffled about why “having unprotected sex behind my back for six months” wasn’t really cool with me.
“If you really love someone, you want to keep them all to yourself.”
This ties in with “jealousy is a super romantic sign of love,” which I’ve ranted about all the issues with before. Nay-sayers use this one to dismiss polyamory as a phase or a thing that people do before they find The One, when it is expected that they will settle down into a Proper Relationship.
Look, if you’re monogamous and feel that, when you love someone, you don’t want either of you to be romantically or sexually involved with anyone else… that is a valid choice! That’s fine! I’m not going to start telling you that you’re just unenlightened or old fashioned or any of that rubbish. You’re monogamous. That’s fine. I respect your choice – please respect mine! Please do not tell me that my love is not real, or that if my partner really really loved me he’d fly into a jealous rage at the thought of anyone else so much as looking at me.
Jealousy is not the surest sign of love. Possessiveness is not the surest sign of love. Living your life in the way that is truest to yourself and your partner(s) and what will make you all happy is love.
 Which usually roughly translates to “hetero and married with children.”