Over-giving drains you, then bitterness grows. Make a boundary that sounds calm. Write one sentence you can repeat: “I can do X. I can’t do Y. I can do X by Tuesday.” Send it, then exit the negotiation loop: no extra paragraphs, no defending, no over-explaining. Protect the space you just created with a 15-minute block for your own priority. Boundaries become real when your calendar reflects them.