A toothache interrupts what should be a perfect afternoon. The sky is clear, but the speaker can't enjoy it, because pain has pulled all their attention inward. In that moment they see "how much / is out of my power": we like to think we're in charge of our lives, yet a small nerve in a tooth can overrule us completely.
The last lines turn the poem in a surprising direction. The speaker calls their body "patient," a word that means both waiting calmly and being a person in medical care, and then compares it to "a great ape." That image strips away the sense of being a thinking, controlling person. What's left is an animal body that simply endures, hurts, and waits for relief. The mood is quiet and wry rather than dramatic. There's no complaint or panic, just a calm, slightly humbled acceptance of being a creature with limits. The bright afternoon makes that realization feel even sharper.