What is unity? Unity is not merely the absence of conflict, it is not merely peace nor harmony. Unity is being as one toward a specific goal or value. It is more evident, and even strengthened, through opposition – externally or internally. David describes brothers in unity as good and pleasant, like the anointing oil for Aaron when he was set apart to be high priest.
It is not enough to be in the status quo..
(And because it is World Cup Season, unity is very like a well playing football / soccer team.)