“Everything is more fragile than it looks. Handle the argument accordingly.”
I'd approach this with measured gentleness: "I need to share something that matters. I've thought carefully about how to say this because I respect what this has meant. Things change in ways we don't always anticipate, and sometimes that means endings we didn't plan for. What we built together had real value—that doesn't disappear. But continuing forward isn't what's best anymore. I know this is difficult. You deserve honesty wrapped in compassion, not false hope. What we're concluding doesn't erase what came before. I'm here if you need to talk through this." The key: acknowledge weight, validate past meaning, accept reality, offer presence.