After Apple-Picking Memory and the Past Quotes Page 2

Just on the basis of his memories of the day, the speaker knows what he will dream about. Strictly speaking, we're pretty sure you can't actually predict your dreams like this. He's making a rhetorical point.

The speaker makes a subtle distinction between active and passive forms of memory. A passive form of memory would be the "ache" that reminds him of standing up on the ladder all day. But he also feels the more active, present memory of the ladder pressing into his foot. He truly is reliving the day again.