In the view that emotions are the "mere" epiphenomena* of biochemical/physiological change, "anger" or "fear" are just the words we use to describe states of the human body featuring among other things relatively high levels of adrenalin in the bloodstream. And "love" is just the word we use to describe the state featuring relatively high levels of endorphins in the brain, among other things!
Among the other things included in "among other things" are the physical activities/behaviours associated with emotions, eg physical aggression in the case of fear or anger. In the extreme view, sexual activities/behaviours are the manifestations of the biochemical state to which one refers by deploying the word "love".
I don't think it solves anything to describe an emotion as a "feeling" or "psychological state": it simply pushes the question out further. And even if we could come up with a clear, tight definition of "feeling" or "psychological state", we would still be no closer to capturing the essential nature of what we experience when we "have" an emotion. This is all very slippery: "experience" = "feeling" = "psychological state", doesn't it? I don't know. I don't know what emotions are. No answers, only questions:
Do the terms "emotional state" and "psychological state" describe the same underlying thing?
In what sense do we "have" an emotion? Or is it that emotions have us? What does it mean to "have" an emotion? Does that imply we should "own" our emotions? Do we / should we take psychological responsibility for our emotions? Attending anger management classes implies an acceptance of responsibility for emotion. Can we "manage" our emotions? Does that mean we can choose to "have" them / experience them?
Are humans the only animals to have emotions?
Is pain an emotion? Is there such as thing as "emotional pain", and if so, what does it have in common with physical pain, if anything?
"Intuition" (another highly problematical word) tells me that emotion is tightly linked to consciousness. I think that emotions are modes or parts of modes of consciousness, or modifiers to modes of consciousness, or flavours of consciousness if you prefer. Emotions introduce color to what would otherwise be a black and white movie of life.
Or is linking emotions and consciousness just shifting the question further out: Is "consciousness" just another word for "feeling", which is another word for "psychological state", which is another term for "emotional state"? And even if we knew exactly how emotions work and how they are produced, that would still throw no light on what they are.
Obviously, being able to control one's emotions can provide a tactical benefit in some contexts. It doesn't always happen but it's conceivable that offering the other cheek after being slapped in the face could change how the slapper "feels about" the slappee, reducing or even minimising the chances of more slapping in the future.
Take the concept of "practice" (eg meditation) in the field of spiritual development. The practice is a means to an end, not the end in itself, unless you want to be a professional meditator.
Perhaps, emotions likewise are the tools whereby the emoter creates the flavour of their personal reality. Emotions are the means to an end (taking mindful responsibility for ones life) not the end in itself, unless you want to be a professional emoter. And so many of us do: we try to be professional emoters, but mainly end up being amateur hysterics! It's easy to become addicted to emotion, in general, or to specific emotions. For example, some people enjoy anger: an acquired taste the acquisition of which carries with it responsibility for the outcomes of the acquisition.
The painting -- 30.5 x 41 cm, oils on canvas, entitled Reconciliation -- was born out of deep emotion. While painting it I experienced a complex of complex emotions, some related to each other, some related to specific people in my life, others relating more broadly, less personally. It's unclear whether the painting produced the emotions or the emotions produced the painting or both. Self-bootstrappy, you might say: inherently unstable but somehow existent.
* Epiphenomena: "secondary" effects. Of course, calling something an epiphenomenon doesn't mean that it's somehow less than real, and that therefore no further analysis is required. It means that the epiphenomenon (the offspring) can be understood only in the context of another phenomenon,the progenitor. It's like the moon, which only reflects the light of the sun, it generates no light of its own. To me that seems like passing the intellectual buck.