The physical truth is that your emotions more control you than you control them. Why?
Because per http://en.wikipedia.org/wiki/Amygdala
, the amygdala, which performs the "....primary roles in the formation and storage of memories associated with emotional events.
",.. "...sends impulses to the hypothalamus for activation of the sympathetic nervous system, to the thalamic reticular nucleus for increased reflexes, to the nuclei of the trigeminal nerve and the facial nerve, and to the ventral tegmental area, locus coeruleus, and laterodorsal tegmental nucleus for activation of dopamine, norepinephrine and epinephrine..." blablabla
The important thing to note is that as neurological pathways are one way and as there are more pathways leading out of the amygdala than there are going in, it is easier for it to control you than for you to control it.
As thinking does form physical neurological connections in the brain, I don't know if it is known but possibly we can develop new pathways back to the amygdala so that we can send it some signals too.
I think the technical term is something your mother used to tell you: "control yourself."
Other structures involving emotions include...http://www.livestrong.com/article/111575-parts-brain-control/
"Two important structures of the diencephalon are the thalamus and the hypothalamus. The thalamus serves as a relay between the cerebral cortex and other parts of the brain. All sensory signals except smell enter the thalamus, and its neurons send them further to the cerebral cortex for processing.
The hypothalamus is involved in homeostasis, or the body's equilibrium, emotions, thirst, hunger and circadian rhythms, or the body's sleep/wake cycle. It also regulates the autonomic nervous system that controls the inner organs. The hypothalamus controls the pituitary gland, which produces hormones that influence other hormone-producing glands.
"The cortex is divided into four sections or lobes. The frontal lobe is associated with reasoning, planning, problem solving, language and higher emotions, such as empathy and altruism
You can deny it all you want, rationalize it away, you can even act against it as best you can, though you have no choice but to "listen" to your figurative heart.