A boundary is a decision you do not have to remake.

Without a boundary, the same request can require a fresh negotiation every time. You reconsider it while tired, explain it while rushed, and feel guilty all over again. The decision becomes an unpaid recurring appointment.

A useful boundary makes your position understandable before the next request arrives. It can still have exceptions, especially where care and real obligations are involved. But an exception should be something you choose consciously, rather than the default result of being asked again.

Which recurring negotiation would benefit from a clear expectation?