The courage to admit a limit can prevent other people from relying on a false promise.

Saying you cannot do something is a service to whoever was counting on you. The reluctance is understandable: admitting a limit feels like failing in advance, so people take on what they cannot deliver and hope the situation resolves itself. Meanwhile others build plans on that yes and find out late, when their options have narrowed; an early no is almost always kinder than a late apology.

If you have quietly overcommitted, say so now rather than at the deadline. Offer what you can genuinely manage and let people plan around the truth.