A border drawn through a landscape does not teach the river to stop.

Lines drawn on political maps cut through landscapes that do not observe them. Rivers, animals, air, weather, and often families continue as they were, which means every border creates a set of problems that can only be solved by the people on both sides cooperating.

The general shape of this is worth keeping. Whenever a boundary is drawn, in a country, an organisation, or a household, the things that cross it do not stop, they just stop being anyone’s responsibility. Ask what falls between your divisions, since that is where the neglected problems collect.