1. "I feel like we're moving too fast."
If a person says this and then suggests slowing down a little bit (maybe seeing/texting each other less during the week or whatever) then they are probably reacting accordingly to things getting serious more quickly than they'd like. Fine! Understandable! If a person says this and then suggests no longer seeing each other at all (or [ugh] "taking a break") then they've realized that they are no longer interested in this budding relationship but would rather end on infuriatingly open-ended terms than risk confrontation.
2. "I don't want to hurt you."
This one is baffling because there exists a vast middle ground between "being in a relationship and hurting someone" and "not being in a relationship and not hurting someone." Part of it is "being in a relationship and not hurting someone"! So it's strange that the person using this line thinks that the person being dumped doesn't understand this? No one who hears this feels grateful for their feelings being spared. They might feel grateful for avoiding dating a turd.
3. "I'm not looking for a relationship."*
On its own, this is a completely valid statement. Not everyone is looking for a relationship, and sometimes people who are both looking for relationships are actually looking for different ones! Different strokes, you know? But it is without a doubt the worst kind of person who says they aren't looking for a relationship, allows the other person to walk away feeling like they experienced an honest and amicable parting of ways with a decent human whom they will think of fondly, and then announces their new relationship on Facebook three days later.
4. "I'm just so fucked up right now."
Hahaha OK, one second, because our eyes will literally never stop rolling. Sure, maybe it's true. Maybe this person is "so fucked up." But first of all, WHO ISN'T? And second of all, maybe stop? "So fucked up" isn't a fixed trait (or even, if we're being honest, actually a trait at all). It's like the person who says, "I know I'm late all the time, but that's just me!" An acknowledgment isn't the end of the conversation. Being late all the time is rude. This statement means nothing. Stop doing it.
5. "I don't deserve you."
This one is so sneakily manipulative, because it seems like it's about how you, as the person being dropped, are an untouchable god among men (which, maybe you are!) but in reality it's about how the other person is working through a martyr complex. It might even lead to the most absurd of scenarios, in which the dumpee actually comforts the dumper! We would never condemn insecurity, but if a person is truly interested in pursuing a relationship with someone who intimidates them, they'll just do what everyone else does (i.e., lie about how smart/funny/interesting they are until they reach a level of comfort at which they can drop it).
6. "I'm just really busy right now."
Nobody who was ever genuinely interested in someone, and in carrying out a relationship with that person, lost interest because he or she had too many meetings that week. "I'm too busy" is an often aggravating, self-important way of expressing something that isn't wrong or illegitimate to feel — if you'd rather not spend any of your free time with someone, that's OK and good to know. But that's about the person, not about the other obligations. Also: Literally everyone thinks they're really busy right now.
7. "I'm just bad at this stuff."
This is one of many self-pitying breakup cliches that sound like admissions of personal failure, but aren't — a close cousin of "I'm so fucked up right now," "I'm just bad at this stuff" romanticizes flaws like inability to communicate, manage one's time, and treat other people with respect. It's one thing to realize you've got some things you want to work on, alone, but it's another to use that recognition as a free pass to flail around helplessly. Being "bad at stuff" isn't just about the person who says it — it also affects the person who has to deal with it.
8. "I still care about you."
This one very much DEPENDS, of course, but saying TOO many nice or seemingly romantic things during a breakup can be confusing. Compliments don't soften the blow, they twist the knife. If you extoll the other person's virtues for too long, in too much depth, they're bound to wonder why, then, you don't want to be together. It's obviously OK to hope you can make peace with an ex, but don't throw out the "I still care about you" line just because you think it'll make a breakup easier to swallow.
9. "I just wish we'd met a few years from now."
And we wish teleportation were real, and that it was eating brownies and not celery that burned more calories than those ingested, and that Lance Bass had been allowed to go to space. But what would the world be like if any of those things were true? We will never know!!! Just like we don't know what it means to wish "we'd met a few years from now." Why are you so convinced you'll have your shit together by then? That seems overly optimistic.
10. "[Nothing]" / Ghosting
Ghosting, or completely disappearing on someone you've been dating for any length of time over a week, is completely gross and totally indefensible. It's thoughtless, lazy, and cruel, and don't let your self-excusing lizard brain tell you otherwise. You know what is the easiest thing to do in the entire world? Texting someone. It has literally never been easier to break up with someone in five seconds. If you can't bring your sad self to do ANYTHING else, say SOMETHING. ANYTHING. Anything on this list is better than nothing.