Should the first letter of these words be capitalized in this sentence or not? I'm quoting them from a poem, and they are not capitalized there. Should I add a comma before "diverged"?
The words "diverged," "both," and "another day" refer to decisions we have to make in life.
No. They should not be capitalized. I wouldn't put a comma before diverged.
Ms. Sue is correct. In a poem, one line seldom is a complete sentence, but is continued in two or more lines. Only the first word of a sentence should be capitalized. Sometimes poems do not use compete sentences, so capitalization is up to the poet, not us to "correct" for him/her. "Correct" rules of grammar often do not apply to poetry. The poet had something in mind, and that's for him/her to decide.
When quoting words from a poem or another written work, it is common to preserve the capitalization as it appears in the original text. If the words are not capitalized in the poem, then you should not capitalize them in your sentence.
Regarding the comma before "diverged," it depends on the context and the effect you want to achieve. In this case, since you are introducing a list of words and phrases, it is common to use commas to separate the items. Therefore, you can add a comma before "diverged" to clearly distinguish each word or phrase.
So, the revised sentence would be:
The words "diverged," "both," and "another day" refer to decisions we have to make in life.