Agreement should clarify what happens when circumstances change.

Most agreements are written for the situation as it stands and go silent about change. Then the circumstances shift, as they always do, and there is nothing to point to except two different memories of what was intended. Building in what happens if things change turns a future conflict into a clause. It is the least glamorous and most useful part of any arrangement.

When making an agreement, ask what happens if either side’s situation changes materially. Decide it now, while both of you are still friendly. That conversation is much easier before it is needed than during.