From Margaret R. Graver's Stoicism and Emotion: "One particularly important class of assents is those called hormai, impulses or action tendencies. From a psychological and moral perspective what matters about action is the mental event that initiates it, and this event can be described as a special form of assent; that is, assent to a proposition of a particular 'impulsory' kind."
"A further Stoic definition of impulse makes it 'a motion of psyche toward something,' namely, toward the predicate contained in the endorsed proposition."
"Emotions are defined by Zeno as 'excessive impulses,' that is, as action tendencies of a certain powerful kind. Since every impulse involves assenting to some impulsory impression, the definition implies that emotions, too, depend on our formulating and ratifying certain propositions about ourselves and our surroundings."