Professional way is to write down what is on your plate right now and then show your boss, ask him which one to prioritize. Tell him you have limited capacity and can only finish some, not all, and put the ball back to his court to help you manage. That's the whole point of having a manager.

If you're a manager position then your job is to help your underling to manage this. If they can't manage means it's your job to get more resource to help distribute the workload, which is where the "manager" position comes in.

Your boss/manager doesn't always know what you're doing.