"Do Not Go Gentle into That Good Night" is the speaker's exploration of what it means to age closer and closer to an inevitable death, especially if the aging person becomes frail and starts to lose his or her faculties. In order to restore power and dignity, the speaker urges the dying to fight their fate and cling tenaciously onto life.
"Do Not Go Gentle into That Good Night" argues that wild, reckless, and passionate behavior, even in the extremes of old age, is wiser than calm acceptance to fate.
In this poem, aging is an inevitable and tragic fate, but this tragedy can be escaped by living as intensely and passionately as possible.