Is there a term I can use to refer to this quote from a poem?

Solution 1:

The term mantra is a possibility.

From Vocabulary.com

mantra

A mantra is a motivating chant, like the “I think I can, I think I can” you repeat over and over to yourself on the last stretch of every marathon you run.

A mantra is usually any repeated word or phrase, but it can also refer more specifically to a word repeated in meditation.

The broadened usage, according to Wikipedia, includes

Definition There is no generally accepted definition of mantra.

  • Renou has defined mantra as a thought ...

The religious overtone may not be exactly what is required.