What to actually say
Open with this, more or less word for word: I had a good time on both dates, but I'm not feeling enough of a spark to keep going, and I wanted to tell you instead of just disappearing.
You didn't do anything wrong, this is just a chemistry thing on my end.
It answers the question they're actually asking underneath the surface one, which is almost always 'was it me?'
I don't have a longer explanation than that, and I'd rather give you the short honest one than make up a longer fake one.
This closes the door on the follow-up interrogation before it starts, without sounding cold about it.
I know that's not a satisfying answer, but it's the true one.
Naming the dissatisfaction out loud takes the wind out of their need to argue you into a better one.
I wish you luck out there, I mean that.
A closing line that isn't an invitation to keep talking still lands warmer than silence.
How it usually goes
A version of the conversation with the push-back left in, because that is the part you need to have already heard once.
What not to say
It's not you, it's me.
It's a cliché people have heard rejected in every rom-com, so it reads as a dodge and invites them to argue you out of it.
We should totally still be friends!
It's usually said to soften your own guilt, not because you mean it, and it leaves them managing a friendship offer they didn't ask for.
I'm just really busy with work right now.
It's a soft lie that leaves the door open, so you'll likely get a 'when things calm down?' text in three weeks.
If they ask what exactly was missing
People often push for a checklist, hoping there's a fixable item on it. There usually isn't, and inventing one just gives them false hope or a false flaw to obsess over. Hold the line without getting cagey about it: 'Honestly, I can't point to one thing, it's just not there for me, and I don't think more time changes that.' Say it once, calmly, and don't restate it three different ways trying to make it land softer. If they keep pressing after that, it's fine to say plainly, 'I've told you what I've got, I'm not going to have a better answer if you keep asking.'
