"...the greatest difficulty, aside from knowing truly what you really felt, rather than what you were supposed to feel, and had been taught to feel..." (Hemingway)
Emotions are to poetry what concepts are to philosophy. Concepts bring precision to theories (the precision of our theories depends on our concepts) and emotions, likewise, bring precision to practices.
That is, emotions are entirely practical entities. They are the "units" of practical mastery. They constitute the texture of our precision in action. They allow us to pass immediately from feeling something in an encounter to acting appropriately.
When I speak of the "appropriate" action, I don't simply mean doing something that is "acceptable" in a social situation. Many of our emotions do have the virtue of such respectability, but not all. Our ability to deal socially with grief, for example, is conditional on the emotions we have available to us to manage in situations where the feeling of loss is present. The mourner and the friend, both, have to draw on their emotional resources to act appropriately. As does the mere acquaintance and the complete stranger when addressing the bereaved.
Everyone feels something when they are around others. Emotions convert those feelings into workable behavior. In some cases, we lack the necessary emotions. The results are familiar.
Some feelings, however, actually require socially inappropriate behavior, and here we require especially precise emotions, which will support very intense experiences.
In any case, our emotional apparatus conditions how feelings are experienced immediately; perhaps more precisely, they make actions immediately meaningful. (Just as a concepts make perceptions immediately meaningful.) Some behavior is not immediately meaningful, and that's simply because we lack the emotions required to attribute a motive to them. (In the case of concepts the problem here is the attribution of sense, not motive.)
The arts keep our emotions working properly, keep them precise. Poetry in particular is the art of refining our emotions in order to keep our experience of social life precise, i.e., intense. The marginalization of poetry (it has been crowded out by sociology and psychology) tells us something important, and distressing, about our culture.
We no longer approach our social relationships through our emotional lives. Most of our actual feelings have become pathologies, or have been outright criminalized. (As Glenn Greenwald has pointed out, the state now wants to control how we express our feelings of, say, hatred.) We have a narrow emotional range. A small set of scientifically constructed emotions. Here "science" does not connote precision; our feelings have been construed as brute "facts" to be expressed in a series of familiar, caricatured gestures. We have become incapable of nuance.