Sam M's poem is about the pain of losing a close friend and the self-doubt that follows. The speaker looks back on late-night laughter, shared secrets and constant conversation, then wonders whether any of it counted, since the friend simply "turned around and left." The opening comparison is blunt: the friendship is treated as if it meant nothing at all.
The speaker keeps asking questions, and they move from the friend to the self. First there is confusion over how "one little fight" could erase so much. Then comes a guess at the cause: perhaps it was because the speaker trusted a boy the friend hated. By the end the questions turn inward, ending with "Was I not enough," answered by a flat "Apparently I wasn't." The mood is raw, hurt and a little bitter. The repeated "not enough" sounds like someone going over the same thoughts again and again. The final lines, saying the friend will never look back, close on a sense of hopeless finality.