It is said that the phrase conveys a powerful message that, when death approaches, one needs to know what made his life meaningful, and he should never fear death. It also affirms the importance of being alive.
I might also say that it is a encouragement to stiffen the spine under adversity.
The irony is that Dylan Thomas died young, less than a month after his 39th birthday.
In any case, it’s a great poem.
Do not go gentle into that good night
Dylan Thomas (1914 – 1953)
Do not go gentle into that good night,
Old age should burn and rave at close of day;
Rage, rage against the dying of the light.
Though wise men at their end know dark is right,
Because their words had forked no lightning they
Do not go gentle into that good night.
Good men, the last wave by, crying how bright
Their frail deeds might have danced in a green bay,
Rage, rage against the dying of the light.
Wild men who caught and sang the sun in flight,
And learn, too late, they grieved it on its way,
Do not go gentle into that good night.
Grave men, near death, who see with blinding sight
Blind eyes could blaze like meteors and be gay,
Rage, rage against the dying of the light.
And you, my father, there on the sad height,
Curse, bless, me now with your fierce tears, I pray.
Do not go gentle into that good night.
Rage, rage against the dying of the light.
Stella's Place 
I had never heard that whole poem. Makes you think.
LikeLiked by 2 people
So many wonderful, meaningful poems out there. This is certainly one of them.
A number of videos have been done with Anthony Hopkins beautifully reciting this poem. I hope he goes with a rage against the dying of the light.
LikeLiked by 1 person