Being done, whatever that means, is great. In my experience, there is a great deal of power, and joy, in having finished what you should. When there is no clear next task, you are free to breathe for a moment, see what comes up in your mind, and pick something to do based on feeling.
So why are our systems designed to completely defeat this feeling and state? We fill our planning to the brim, we build backlogs, and if anything the goal is to minimize the chance of this ever occuring. Always having a next task may be good to minimize decisions and for chewing through simple things, but I think it robs us of a feeling of accomplishment, of being caught up, too often.
For myself, I have tried to go somewhat the other way in how I try to plan, keeping my list of things for a day as short and simple as possible in order to get to this state faster. When that list is completed, I can relax. And this often means I enjoy picking up something else and getting that done.
Getting things done is aiming for this too, in a way I did not quite realize at first. It really wants you to be in this state every time you finish a task. You should always be just the one current task away from being done, and then be in the state where you pick a next thing by making an intuitive decision without worrying about other things.
But I wonder if something is not missed by not having a quite reachable goalpost of sorts for the day. "The important stuff is all taken care of, now I can have some fun."