In sickness and in health.
Getting sick is a fairly effective event for putting things in perspective. Even when the sickness isn’t severe or life-threatening, there’s nothing like a little taste of your own mortality to make you question the way you’ve been living your life.
If no one ever got sick, the world would be a very different place. The simple knowledge that one day, you will die, is not nearly salient enough if you never personally experience anything that gives you a glimpse of that knowledge. If no one ever got sick, hubris, bravado, and grandiosity would likely skyrocket (as if they aren’t prevalent enough). In that respect, humans being in touch with their own mortality, to a certain extent, is probably a good thing.
Steve Jobs would look in the mirror every morning and ask himself, “if today were the last day of my life, would I want to do what I am about to do today?” This is an excellent way to keep your own mortality salient, thereby facilitating reflection and reprioritization of objectives, and ultimately, living a life without regrets.
My existence in this world is temporary and transient. My days are numbered. Don’t waste your time chasing after items of impermanence. Strive for meaning in a meaningless world.