When someone you care about leaves suddenly and you never get a chance to really say goodbye?
When someone you care about slowly degrades over time, until they reach a point when they are no longer the same person you once knew?
I've had to deal with both in my life, and I really don't have a perfect answer. Maybe there isn't even a good answer, let alone a perfect one. Maybe both are a means to an end, knowing that the journey will not be pleasant either way. I do know that age brings the ability to handle either better, although I do suspect that the degradation part/choice is far more cruel for all parties concerned.
"Degradation", now there is a word and a half.
I think that as we all grow older, we have to make a fundamental choice in our lives. The first choice is to grow wisdom with age, facing the future as an opportunity to leverage our life-experience to learn even more. The second choice, I suspect, is to cling onto the past as if life is just lived in the rear-view mirror. Ultimately, maybe this is the key difference between those who grow or those who decay in front of our eyes is this: our choices as to whether or not we want to learn more.
Now I'm not so naive as to think that all learning is a positive experience. Just stick your finger into a powered light socket to understand what I mean. And that is just physical pain. In my experience, physical pain is far easier to overcome than the emotional variety, but that's just me. Anyway, emotional pain has a tendency to gain deeper roots in your head; think about it: we all remember the feelings associated that relationship which ended in a particularly bad manner. That toothache from two years ago? Maybe not so much.
Back to choices. Yes, in the end, this is about choices. As those great Canadian philosophers of modern progressive rock, Rush, once said: "if you choose not to decide you still have made a choice". They were right. Viewing the present and future as full of opportunities to learn is a choice. If you fail to make that choice, you are choosing, in my estimation, the path of decay, and your family and friends will have the honor of watching you slowly rot over time. Maybe zombies are real after all.
None of this is easy, and I don't think it there is such a clear line of demarcation between the choices we make in the short run. Yes, I think we all make short-term decisions that are sometimes not in our best interest, but that's the nature of small decision making. If those small choices take us off the path of learning and growth it's usually pretty easy to correct ourselves, especially if we have family and friends who are there to provide perspective. What's more, I think people who are inherent learners in life are good at auto-correcting when it comes to bad choices. In time though, I do think the lines between growth and decay become pretty clear. for everyone. It's as clear as the choice between, for example, alcoholism and sobriety. I know that it's not easy to overcome alcoholism, by the way, but it can be overcome. That's a choice.
No amount of philosophy helps though when it comes to watching someone we care about rot before our very eyes. It's a kind of long goodbye that all of us probably hate in more ways than one, especially when it simply didn't have to be in the first place. That's the "rub", if you will: we don't make overt choices about things like getting Alzheimer's, but far more we do make choices about how we respond to much of what is around us and inside our heads.
Me? As clearly imperfect as I am, I fully intend to go to my grave reading, learning and experiencing life to the best of my ability. My children will not see me rot in front of them as I grow older. I just wish the same where true for others.