Learn
Conflict usually escalates through distance: notes instead of conversations, complaints to a third party instead of the person. Proximity de-escalates.
Lead with the impact, not the accusation. 'The music carries into our bedroom after eleven' invites a fix. 'You're inconsiderate' invites a defense.
Aim for a workable arrangement, not agreement. You do not need to see it the same way to live next to each other well.
Reflect
Is there a small irritation you've been storing up rather than naming?
Try it
Have one in-person, low-stakes conversation about something small before it grows.
Somewhere real to practice this
Choose one. Nothing is sent to them — this is just for you.