A lot of this is culture dependent I believe, but i am under the impression that at least on western countries you cannot do this a lot of times without a high cost, specially if you re not a manager. If someone comes to your desk directly, you are supposed to stop what you are doing and give your attention to that person, even if you are working on something really urgent. Refusing meeting requests is also not well…
This is company dependent rather than country. When I was early in my career as a software dev I felt like I could never say no. I would continue to take on additional work which translated to more hours. Eventually my manager at the time did the best thing he could for me. He asked me into his office for a "talk". Then he told me that he didn't want to lose me because I burned out. He said, "Look, you have to learn…
Where I work, the entire culture changed from "let's work together to make everything better" to "you drop everything RIGHT NOW if the boss decides that they have a personal project" when a new one took over.
...and so I will be starting my new job in a couple of weeks.