Just a quick thought.
I do think it is valuable, in planning your day, to identify which tasks are “A” priorities for that day and which tasks are “B” or “C.” Prioritizing can be done wrong, but I think it is helpful in general.
Here’s a nice outcome of this: If you identify “A” and “B” tasks, then when you are done with your “A” tasks, the rest of the day has lower pressure. You can be more free to be interrupted because these tasks aren’t absolutely essential for the day (they are “B” priorities for that day), and yet it feels like you are getting ahead with whatever you do get done.
I don’t think it’s good to have your whole day consist simply of pre-defined tasks and appointments. But it’s hard to get around the need for some sort of list. This helps you keep that list from becoming a tyrant rather than a tool and servant.