Like all matter, that of our physical body is subject to time, and it wears out. This is what we call growing old, and we all grow old, which, of course, is not particularly pleasant.
But we are not just a physical body, and if the wear of the body is in the natural order of things, internally, nothing forces us to grow old with it. Therefore, instead of becoming upset about the physical manifestations of age, humans should be concerned with nurturing that which always keeps them young and alive: their heart.
It is their heart, their capacity to love, not their body, that makes humans young or old, and if their heart ages, it is because they allow it to. How so? By losing their love for people and things, by losing their curiosity and their interest for the life that abounds all around them, the rich and abundant life of the universe.
But if they strive to feel this life, if they seek to participate in it, to introduce it into themselves, they will not grow old.