What you have is an obligation to live a life that results in 1) you still finding meaning in what you are doing despite your old age and 2) that contributes something back to those around you, even in your old age.
At the end of the day, humans need to feel like that have responsibility / are making a difference (generalized statement I know) to feel their own life has much meaning. Just because you become a burden due to frailty or sickness does not mean you are unable to benefit others still.
Selected Cicero[1]: "But bear well in mind that in this entire discussion I am praising that old age which has its foundation well laid in youth. Hence it follows— as I once said with the approval of all who heard it— that that old age is wretched which needs to defend itself with words! Nor can wrinkles and grey hair suddenly seize upon influence; but when the preceding part of life has been nobly spent, old age gathers the fruits of influence at the last."
But it is our duty, my young friends, to resist old age; to compensate for its defects by a watchful care; to fight against it as we would fight against disease; to adopt a regimen of health; to practice moderate exercise; and to take just enough of food and drink to restore our strength and not to overburden it. Nor, indeed, are we to give our attention solely to the body; much greater care is due to the mind and soul; for they, too, like lamps, grow dim with time, unless we keep them supplied with oil.
Those, therefore, who allege that old age is devoid of useful activity adduce nothing to the purpose, and are like those who would say that the pilot does nothing in the sailing of the ship, because, while others are climbing the masts, or running about the gangways, or working at the pumps, he sits quietly in the stern and simply holds the tiller.
He may not be doing what younger members of the crew are doing, but what he does is better and much more important. It is not by muscle, speed, or physical dexterity that great things are achieved, but by reflection, force of character, and judgement; in these qualities old age is usually not only not poorer but is even richer."
[1] - has select quotes from Cicero on Old Age: https://newsletter.butwhatfor.com/p/takeaway-tuesday-on-old-...