How do I stop my friends & relatives from postponing their requests for help until the last minute and then disrupting my plans with urgent requests?
The problem outlined in the title is really getting to me. Some of my relatives and friends are overburdened by their everyday duties and barely manage to plan ahead. They often suddenly face an imminent deadline and need my help to meet it. They ask for help with school or university homework, computer tips, translating a short text, writing an important email, etc. Helping them usually takes just half an hour or so, sometimes extending to an hour or a bit more. However, the urgency of these requests disrupts my plans, as I'm usually on a tight schedule. Even though they are clearly at fault, saying no is not an option for me because of the consequences of missing the deadline for them. It's just an inconvenience and disruption for me but a significant loss for them if I refuse. Yet, their requests usually could have been made earlier, allowing me to find a convenient time to help. I've tried talking and explaining the issue, but to no avail. They seem so overburdened that they can barely plan ahead, let alone consider my comfort. I must do something, but what? They are my friends and relatives, not just coworkers. Is there any effective strategy to resolve this issue? UPDATE: Saying no could undermine the friendship. I also ask them for important favors, though never at the last minute. If I say no, they might do the same. If I make excuses, they will, too. This has happened before. I am happy to help them; I just want to ensure they don't wait until the last minute to ask. Is there a way to achieve that without saying no or threatening to?

The problem outlined in the title is really getting to me. Some of my relatives and friends are overburdened by their everyday duties and barely manage to plan ahead. They often suddenly face an imminent deadline and need my help to meet it. They ask for help with school or university homework, computer tips, translating a short text, writing an important email, etc. Helping them usually takes just half an hour or so, sometimes extending to an hour or a bit more. However, the urgency of these requests disrupts my plans, as I'm usually on a tight schedule.
Even though they are clearly at fault, saying no is not an option for me because of the consequences of missing the deadline for them. It's just an inconvenience and disruption for me but a significant loss for them if I refuse. Yet, their requests usually could have been made earlier, allowing me to find a convenient time to help.
I've tried talking and explaining the issue, but to no avail. They seem so overburdened that they can barely plan ahead, let alone consider my comfort.
I must do something, but what? They are my friends and relatives, not just coworkers.
Is there any effective strategy to resolve this issue?
UPDATE: Saying no could undermine the friendship. I also ask them for important favors, though never at the last minute. If I say no, they might do the same. If I make excuses, they will, too. This has happened before. I am happy to help them; I just want to ensure they don't wait until the last minute to ask. Is there a way to achieve that without saying no or threatening to?