Not all tasks/responsibilities count as “balls” in this metaphor. Continuing with the hike example; the teacher’s task list might include
Drink water
Avoid trail hazards like poison ivy
Stop for a snack
Talk about different plants
Answer student questions
None of which count as a “ball”—you do as much of the “nice to have” stuff as the (time/energy) budget allows after ensuring that no student gets lost.
There are a few members who prefer a serious tone and down vote all attempted humor.