Health in old age is something that you invest in, much the same as wealth. Of course you can suffer an accident, or lose your investments from bad luck. But in both cases you're guaranteed bad results if you don't put the effort consistently and starting when you're younger.

For health, this means making exercise, good sleep, and good diet a part of your daily routine. Much like investments, you can go as deep on that as you like, but if you start early all you need is basic knowledge.