Imagine a study partner asks, "Can you finish all six summaries by tomorrow?" If that is not realistic, avoid an uncertain yes that the other person will treat as a commitment. Try, "I can finish two by tomorrow, or all six by Friday."
This response offers a choice between scope and timing. It is more useful than "I am too busy" alone because the group can decide which result meets its actual need.
Define what finished means
Clarify the expected stage: "Do you need rough notes for discussion or a checked final version?" Those are different tasks. You might be able to provide all six rough summaries tomorrow without being able to promise six polished ones.
Practice reaching an agreement: Partner: "We only need notes for Thursday's meeting." You: "Then I can send six short outlines by Wednesday evening. I will revise the selected two after the discussion." The final arrangement includes both deliverable and timing.
Check that any deadline change is accepted by the person or process responsible for it. A suggestion is not an approved extension. End by repeating your commitment accurately, including conditions that remain. This language is useful for ordinary collaborative tasks because it makes capacity visible and allows a practical decision without turning every request into either an automatic promise or a complete refusal.