I chuckled at this poem. This is a brillant short write. From the title to all three lines, everything is spot on.
The title: Existing in life could be seen as irony a bit, because if you actually think hard enough we live to just die in the end. And i think death could be seen as joyous, or a celebration of life, so it's one big circle really.
Line one- i love the how you used the word Nihilism, after using the title you used, because to me they fit together well. I think depending on the person you ask life could be seen as meaningless.
Line two- I do like this line a lot and its probably my favorite here, only because it sets up the last line and enhances the first line well. I do like the word plague here, because that tells me that this has been "harming" or bothering you for a long time.
Line three- This is line wraps up the poem nicely in my opinion. This line fits the first one hand in hand, and that is why this poem is clever and brilliant. To anyone that doesn't understand the terms here could say this is sarcasm. But i enjoyed this poem because there is really one meaning here and it's difficult to write a meaningful poem in 3 lines.