Breakups don't have a universal script, but decades of bad ones have produced a reliable list of phrases that make a hard moment harder. “It's not you, it's me” has become a punchline precisely because it so rarely lands as reassuring — it reads as an obvious dodge, which invites exactly the follow-up question it was meant to avoid.
Comparisons are another reliable mistake. Bringing an ex, a crush, or “someone better” into the conversation turns a breakup into a rejection contest, and the other person will remember that detail long after they've forgotten the rest of what you said. Similarly, don't use the moment to relitigate every unresolved grievance from the relationship — a breakup conversation isn't the venue for a comprehensive audit.
What tends to land better: clear ownership of the decision (“I've decided,” not “I think maybe we should probably”), one or two honest and specific reasons rather than a list, and something acknowledging the good that was real, if it was. “This isn't working for me anymore, and I don't see that changing” is plain, but it's also unambiguous, which is its own form of respect.
And afterward: don't ask them to affirm you're a good person, don't ask for a hug that isn't wanted, and don't linger. The kindest exits are clear and reasonably short.