As a Supervisor, my responsibilities are often not tied to specific dates and times. Sure I have scheduled meetings, etc. but most of what I do simply needs to be done before "X date" instead of a very specific time. This allows for a fair amount of flexibility in setting up my day-to-day activities, but it also requires careful planning and constant adaptation to changing priorities.
Eventually it always feels like there is either:
way too much work and not enough time
... or ...
plenty of time and nothing that has to be done right now
Given the choice, I prefer the "Feast" (where I am just so busy that I have to raise my performance to meet the challenges of fitting everything in). Although, it is nice to have the "Famine" (ample amounts of "down time") periodically.
I think the biggest challenge that I personally face is that I'm often looking forward to whatever is coming as opposed to enjoying the here and now. When I'm "swamped" I think about how nice it will be when I'm caught up. And when I'm in a lull between things I look ahead to busier days and get excited for the challenge that is coming.
Maybe if I planned better I would be able to even these peaks and valleys more ... but I think that the scenery would then be boring, even if it were more comfortable. Talk about your no-win scenario! :)