III.D17: Biting of Conscience Defined

Conscientiæ morsus est tristitia concomitante idea rei præteritæ quæ præter spem evenit.

Biting of conscience (or remorse) is a sadness accompanied by the idea of a past thing which turned out beyond hope. 

Here we have a hope unmet and Spinoza uses a phrase that exactly describes the physical sensation - consistent with the concept that the mind is the idea of the body and, thus, bodily-centered.