It's impossible for me to stay upset when I am taking a hot shower.
I always assumed the bodily manifestations of my emotions (crying) were the result of the mental (feeling upset) --- it's actually the exact opposite; I am upset because I am crying.
Let's start with William James:
"Our natural way of thinking about these standard emotions is that the mental perception of some fact excites the mental affection called the emotion, and that this latter state of mind gives rise to the bodily expression. My thesis on the contrary is that the bodily changes follow directly the PERCEPTION of the exciting fact, and that our feeling of the [p.190] same changes as they occur IS the emotion. Common sense says, we lose our fortune, are sorry and weep; we meet a bear, are frightened and run; we are insulted by a rival, are angry and strike. The hypothesis here to be defended says that this order of sequence is incorrect, that the one mental state is not immediately induced by the other, that the bodily manifestations must first be interposed between, and that the more rational statement is that we feel sorry because we cry, angry because we strike, afraid because we tremble, and not that we cry, strike, or tremble, because we are sorry, angry, or fearful, as the case may be. Without the bodily states following on the perception, the latter would be purely cognitive in form, pale, colourless, destitute of emotional warmth. We might then see the bear, and judge it best to run, receive the insult and deem it right to strike, but we could not actually feel afraid or angry" (What is Emotion?).
The theory is that we have reflex physical reactions to a situation, which stirs up certain emotions. So my becoming upset is actually a result of my FIRST feeling physically upended, trembling, crying, etc.
Let's take this to the next step then.
James more or less proves my theory of "fake it 'til you make it" as being valid. When I need to be confident for a class presentation, I pretend to be and I am. When I am feeling morose and want to snap out of it, I pretend to be happy and I become happy. As James says, the "voluntary path to cheerfulness...is to sit up cheerfully, to look round cheerfully, and to act and speak as if cheerfulness were already there" (The Gospel of Relaxation). Why? Because emotions are just the result of our physical state. So to change our physical action is to change our feelings -- "...action and feeling go together; and by regulating the action, which is under the more direct control of the will, we can indirectly regulate the feeling, which is not" (The Gospel of Relaxation).
We are the combination of our body and our mind. BODY + MIND = US.(D&C 88: 15 spirit and the body are the soul of man)
So when I climb into a hot shower and relax my body -- the emotion of being upset is no longer being stimulated by my physiology. In fact, as my physical state is changed by hot water and steam it results in my no longer being upset. It's not my emotions that are in charge. It's still ME -- because I choose how to change my physical state.
That's why deep breaths help when you are angry and hugs help when you are sad.
That's why I AM IN CONTROL of my emotions. Even when I think I am not.
While I don't agree with all of his points, in The Feeling of What Happens Antonio Damasio makes an interesting argument for the evolution of emotions (excerpt here).
Also NPR's Radiolab does a bit on emotion and physiology in connection with phantom limbs (listen here).