I'm not that old, but I'm old enough that I have friends who are eyeing retirement. I also have friends who are eyeing University graduation, and while I know which side of the scale I'm closer to, I can see the similarities. Those who are approaching graduation have a world of opportunity ahead of them so vast they can be paralyzed by indecision. The same is proving true of those who are approaching retirement - there's a world of possibilities ahead of them, and there are a thousand reasons why they will explain how those possibilities are unattainable.
There is always something to say "no" to at every moment, but during the big transitions in life, you should be saying "yes" to everything. Bill Gates and Mark Zuckerberg both dropped out of University because their companies were already starting to fly. They had something to move towards - something to say "yes" to, and completing their education was going to be a barrier, not a benefit. Graduates and retirees should similarly have something to move towards. The act of graduating or retiring shouldn't be destination but a disembarkation point. If a graduate or a retiree is unprepared for what comes next, they are missing the true meaning of the moment - but if they have something to move towards, they will find it growing quickly on the approaching horizon, and it will deliver inspiration, purpose and meaning.
I didn't finish my Master's degree in English Literature, even though I finished the course work. If I had just submitted a thesis, I would have an M.A. I write 80-page reports all the time now - why didn't I just write the damned paper? I don't know if it would have helped me in life, but I will never know which opportunities I may have missed for not having it. And I was so close. It bugs me that I didn't have the determination to see it through, but any meaning I ascribed to the degree faded once I had a job. It never occurred to me that I might have landed an even better job if I had just invested a few more months in the degree. I didn't have a plan in place for something to move towards - I said "no" instead of "yes," and that probably made a difference.
University degrees open doors, and retirement should open doors too, not close them. Open doors are opportunities for growth, and they are better faced with some careful consideration. The journey pursued to that door's threshold is what defines a person in that moment. Understand where you're going by understanding where you've been, and move purposefully towards something important. At the end of the journey you followed to get to that door, doesn't it seem like a seem like a sin if you don't exit it at a gallop - knowing with complete confidence that you are flying in the right direction?