State the limit while you can still state it without trying to hurt someone.

Limits held too long stop being information and start being weapons. Said early, a limit is just a fact about you, delivered without heat and easy for someone to work around. Said after months of quiet accumulation, the same sentence arrives carrying everything it has collected, and the other person hears an accusation rather than a boundary and answers that instead.

Name the thing you have been tolerating while you can still say it kindly. If you notice you want the sentence to land hard, that is the signal it has waited too long, and one more day of thought is worth it.