Sharing is Caring – Combating Unrealistic Demands

A good way to help yourself is to make your work load visible to all requestors. If they have the same understanding of that as you do, it makes the conversation more objective. It also helps to have your manager on board with your understanding of priorities so that if you are asked to do something which doesn't align with those you know that they have your back...

Kiron

I do agree with Kiron.
Sharing your priorities with others may help.

As Kiron said, stablishing priorities is a good manner to manage multiple simultaneous requests. Also, with your experience you can determine the amount of effort for similar work, and can give your manager an adequate stimate of the completion.

Sharing priorities is good, but also consider who is asking in how you reply.

If it is someone with no direct authority over you, I would share your priorities at a high level, without providing so much detail that they try to re-prioritize your workload for you. I would also provide an ECD for when you will be able to address their request.

On the other hand, if it is someone like your senior VP, you may get your priorities "adjusted" for you. That may mean you are pausing something urgent, in which case you should disclose what other high priority work must wait for this new demand. They may change their mind if the existing priorities are more urgent than the new action item.

Taking a cue from the experiences and what has worked for me well is to take a step back. Do not be reactive. I believe in cause and effect . If someone is coming to me with something that needs to be done immediately I first try to get the reason for urgency. Will not set a meeting for it but a quick chat on why this needs to be done now. The intent is not to challenge but to evaluate the options and see if I can buy sometime to provide the expected. Most of the time during this quick chat it turns out that there is no urgency or the reason is not clearly known. The reason sometimes can be " someone else told it's urgent".
If the reason is clear and there is an immediate action required, then I do mind mapping of impact in taking it up and inform all stakeholders with a note that there is an immediate action needed and I will get back with impact asap.
Most of the time I get someone from stakeholders pitching in trying to negotiate on the urgency or provide options to reduce the impact.
Finally if majority agree and it's unavoidable, then proceed with next step of adjusting the priorities and proceeding with the new action.

All this seems to be lengthy and time consuming, considering immediate action expected but with the right communication, this can be made viable in a matter of 3 to 4 mails getting a buy-in from stakeholders as well to adjust the priorities.