Cher Calderilla's "Determination" is built on a list of denials. The speaker says over and over that she didn't write the poem to flatter a man's style, to praise his face, to make him phone or text her, or to comfort him about the women he's lost. Each "I didn't" lets us see exactly what she's refusing, and also how much attention she has paid to him: the oversized shoes, the tired eyes, the movie-star voice.
Then the poem turns to a fierce, wary woman, "the most brazen creature" the speaker knows, always watching for threats, even from the speaker herself. The speaker admits she is "prone to lighting those matches" too, so she understands that urge to destroy.
The ending reveals the real purpose. She wrote the poem to remind herself she can still appreciate what is tremendous in the world. The mood is guarded and tender at once, and the last line lands with quiet force: writing about someone else becomes a way to save herself.