The speaker admits they were sure of themselves. They had a plan and believed they understood how things would go, but the poem keeps circling back to the same blunt confession: "I was wrong." What shatters that certainty is another person, who arrives and changes everything.
The feelings the speaker describes are small and physical. They are "hot faced" and blushing at every smile and every laugh, until the list collapses into "Every everything," as if ordinary words can't hold the rush. The repetition of "I thought I knew" makes the speaker sound a little dazed, going over what happened and trying to make sense of it. The ending, with its twice-repeated "I didn't," feels both humbled and quietly amazed.
The mood is shy, giddy and slightly unsteady. It captures the moment of falling for someone and realizing that control was never really yours. The title hints at a gesture of letting go of something, though the poem itself doesn't spell out what it means.