The question are related to the text below
The poet Dylan Thomas wrote that one should
not go gently into that good night, that old age
should burn and rage at close of day. As a younger
man reading that poem, I saw futility ∈ those
[5] words. I saw aging only as a failing: a falling of
the body, of the mind, and even of the spirit. Isaw
my grandfather suffer aches and pains. Once
agile and proudly self-sufficient, by his sixties he
struggled to swing a hammer and was unable to
[10] read a label on a box of Triscuit crackers without
his glasses. I listened as my grandmother forgot
words, and I cried when eventually she forgot
what year it was.
At work, I watched as people neared retirement
[15] age, the spark gone from their eyes, the hope from
their smiles, counting the days until they could
walk away from 1t all, yet with only the vaguest
plans about what they would do once they had so
much free time, all day, every day. But as I've
[20] grown older myself, and have spent more time
with people who are 1n the last quarter of their
lives, I've seen a different side of aging. My
parents are now 1n their mideighties and are as
engaged with life as they have ever been,
[25] immersed ∈ social interactions, spiritual
pursuits, hiking, and nature, and even starting
new professional projects.
Adapted from LEVITIN, Daniel. Sucessful aging: a neuroscientist explores the power and potential of our lives. New York: Dutton, 2020.
According to the text, what is the author's main concern?