"A useless life is early death" (Johann Wolfgang von Goethe).
WANTING TO BE USEFUL IS AN IMPORTANT PART OF OUR NATURE. We may be easily distracted from that desire -- and some folks seem to have suppressed the urge altogether -- but still it's true, we want to feel that we're of use to somebody. Times of enforced idleness, such as periods of illness or disability, are rarely the times we remember as the happiest points in our lives. "It is a great misfortune to be of use to nobody" (Baltasar Gracián).
In regard to this "misfortune," however, there is something we need to be aware of: it is never actually the case that we are "of use to nobody." We may feel useless sometimes, but that feeling is never entirely consistent with reality. My father, for example, who just celebrated his ninetieth birthday, struggles with feelings of uselessness from time to time. Physically, he's quite limited in what he can do, and it's often hard for him to see any real purpose for his continued existence in the world. Yet in truth, he continues to be useful to others in ways that he's not aware of. If nothing else, his example of steadfastness and good cheer is of great value to all who know him.
It's an obvious fact, of course, that our usefulness can be diminished by circumstances beyond our control. But usually, what is diminished is only our preferred and customary way of being useful. What we need to do is let go of the past and have the humility to switch gears. We need to adjust ourselves to new ways of being useful -- ways that may be less congenial to us but are no less valuable to others.
In the real world, there will be few days when we can't do something that somebody else needs to have done. We can be useful if that's what we want to be, and it's a great thing to set that as our goal. An even greater goal, however, is to combine usefulness with grace. We can diminish the amount of drabness in the world by (1) doing what needs to be done, and (2) doing it in such a way that delights and encourages those whom we serve. Pragmatism and practicality are commendable qualities in their own right, but they're nothing short of astonishing when they're clothed with the added quality of grace.
"The difference between utility and utility plus beauty is the difference between telephone wires and the spider's web" (Edwin Way Teale).