But it's also a good warning to carry with you when things aren't bad. When things are going just great, actually. Everything's coming up aces, and the world is nothing but sunshine? Enjoy it, but prepare yourself for when that all goes away, because one way or another that's going to happen--maybe tomorrow, maybe decades from now, but it ain't going to last.
I have one surviving grandparent at this point in my life, and she's begun the slow slide into being unable to care for herself. As I'm watching my dad and his siblings try to manage logistics and the various emotional tensions that almost always happen in such situations, I'm also trying to mentally brace myself for when he's in the same place. For when my mom's not around anymore, and suddenly there's no one to lean on. Not to sour the good things I currently have, but to savor them while they last, to warn myself that my parents aren't in fact fundamental to existence, not even mine.
Yesterday it rained. Today the sun is out, and it is glorious. Tomorow it may rain again. All things come and go. Some of them may come again; most won't. Such is the way of life.