You're going to cry and that's fine. I think the trick is accepting that instead of trying to avoid it. I wrote mine at 2am the night before submission and it was just pure emotional exhaustion on a page. But my advisor said it was the most authentic part of my whole dissertation lol. A practical thing: write a list first.
Just bullet points of names and specific memories. "Dr. Smith—read my drafts on weekends." "Jenna—kept me fed." Then turn the bullets into sentences. It's less overwhelming that way. Also don't worry about leaving people out. Everyone who matters knows they mattered. The acknowledgments aren't a legal document. They're a moment. You're allowed to be imperfect in them.