#fixes everything

But no. "It's not fate". It's. It is not.

They could have had him say "It isn't fate that we met, I'm not special, anyone could have been so lucky, and one day she'll realize that" as was supported by the context (and the reason I misremember it). Instead, they had him say "It isn't fate that we're together now. It isn't destiny for us to be together. It's just dumb luck. Anyone can fulfill that role for her. And soon she'll realize that too", 'she's already started to' as is said in the original script.

His words are insults. No doubt about it. But they didn't have him insult the past, something he can reframe (to make it consistent with when he does in his speech to her later). They had him insult the present. That isn't about reframing and retrospect. That's what he feels now. He didn't call meeting her dumb. He called dating her dumb. They switched tenses in the MIDDLE to make sure of that.

Such a small change. They didn't make.

He thinks their relationship is dumb but for reasons he is desperate to hide. He thinks it's dumb but that's grounds for him to keep it, not end it. It'd be grounds for her to end it. She loves him, but he's not irreplaceable. He's praying she doesn't notice because to him, she is. A boyfriend who will love her is easy to find and as soon as she realizes that she'll stop settling for one who can't and leave him, looking around or waiting for someone who can. But a girlfriend who shields him from questionings like "You called a couple of times. It's been a year, Mike. Meanwhile El has like a book of letters from you" is dangerous to disappear for even a second.

Just like how he knew he loved her before he let it slip out in front of people in an emotional moment of fearing losing her, he already knew he thought their relationship was stupid and over too. He just knew if anyone ever heard him say it, they'd hold him to it, because those are the kinds of words a better person considers actionable.