So long as they are young and in good health, people never think about the principle of disintegration

"So long as they are young and in good health, people never think
about the principle of disintegration at work inside them, which
will eventually prevail. They tend to think the world belongs to
them and the future will never stop smiling on them. How
disappointed they are when they feel everything beginning to
elude them on the physical plane! In the merciless struggle
taking place between the principles of life and of death, there
are those who want to hold onto life by any means possible, with
the result that they may act in the most senseless ways, throwing
all the resources into the battle that they should be using for
their spiritual work, and then they lose everything.
We did not come down to earth to remain young and healthy
forever but as a training, an apprenticeship. The wise person
knows the bends in the road and strives to make use of
everything. In the spiritual world, upward progress is
continuous. Down here, whatever we do, we will gradually see our
forehead and cheeks become wrinkled, our hair grow white, our
teeth fall out, and so on. But you must understand that the outer
appearance is of no importance when radiant spiritual life shines
through the white hair and the wrinkles."

Omraam Mikhaël Aïvanhov