That is a bad idea. Some of those balls in the air are things you should be doing but can skip. Exercise is a perfect example - we all know that it is important for good health, but it is also something that if you skip a day here and there it is okay (just don't let one day skipped lead to a week). Similarly I practice my musical instruments, but I often skip that when something else comes up, but I have no interest in not having practice as a ball in the air even though I drop it more often than not.
Life only rarely goes perfectly to plan. You will have to change plans at the last minute because of emergencies, but planning to do nothing just in case there is an emergency is a bad plan. Your boss will ask you to work late. Your kids will get sick. You will get invited to a last minute event. It is likely that you will be involved in two different activities that schedule an event at the same time. All of these are a sign of a fulfilling life, not of a problem.
Fulfilling for some. A system without slack is a brittle system.
I really have nothing more to say but I manage to find slack, and when life throws me a new ball to juggle I can deal with it, and use the spare time, energy, and focus to deal with them properly -- rather than become winded, stressed, and pressed.
I have always tried to find fulfillment with less, rather than more. The people I see zipping around from thing to thing have superficial and shallow experiences. Then they end up being superficial and shallow people. Chicken or egg?
However, nothing is more irritating than having to personally deal with the "zippies," high on whatever stimulant (caffeine, nicotine, amphetamine, etc.) so they can have the "energy" to "deal" with life's "responsibilities."
There's something to be said about work ethic, being able to push yourself to your limits, and balance on the razor's edge -- there is something special in that. However, lacking any sort of overarching focus is a much more common and base state of being. "More must always be done!" Yet they haven't taken any time to step back and reflect if what they're doing is even worth anything -- even the ancient generals figured that out.
It's an inefficient allocation, in my view. I consider exercise (and a few other things) to be necessary to sustainably perform at a certain level.
I don't see them as merely enriching things, but necessary things in order to maintain my spirit (body, mind, and soul). In the vein, they gain priority over everything else. If life comes to a point where I have to sacrifice the things that keep me going (say for instance sleep, food, sunlight, and social interaction; for you it might be family), then I must figure out how to get rid of the other "balls" ASAP with the least amount of cost. And once that's taken care of, were they really that important if they're so easily disposed of?
If you lose your spirit, or let it wither by a thousand cuts a la burnout, what do you have left?
Exercise is needed I agree. However skipping an occasional day is not a problem - in fact rest days are sometimes helpful. I've already decided to skip today because it is raining. Of course if I lived where it rained everyday I'd have to find a different option, but since most days are sunny I can just skip a day without harm.
Life only rarely goes perfectly to plan. You will have to change plans at the last minute because of emergencies, but planning to do nothing just in case there is an emergency is a bad plan. Your boss will ask you to work late. Your kids will get sick. You will get invited to a last minute event. It is likely that you will be involved in two different activities that schedule an event at the same time. All of these are a sign of a fulfilling life, not of a problem.