Transience in "Do Not Go Gentle into That Good Night" causes the speaker a lot of anxiety. It worries him that there are things people might have been able to do in the world if only they had been here longer. It bothers him that the sun travels so quickly across the sky and that people live such a short time. But even though transience is disturbing, it also creates opportunities for beauty.
The tragedy of "Do Not Go Gentle into That Good Night" is that nothing can last – neither nature, with her sunrise and sunset, nor man, with his "frail deeds," can ever create anything permanent.
Even though most of the things described in the poem are subject to the ravages of time, there is one thing that lasts – the power of man's words, which persist even after the speaker is gone.