1. A mental state that arises spontaneously rather than through conscious effort and is often accompanied by physiological changes; a feeling
2. A state of mental agitation or disturbance
3. The part of the consciousness that involves feeling; sensibility
The brain is a complex piece of muscle tissue that is composed of tiny brain cells called neurons. These neurons have tiny branches that reach out and connect to other neurons to form a neuronet. When we're born our brains are pretty much a blank slate. Based on the input we are given from our parents, peers, and environment our brain creates its neuronet. That neuronet defines the way we act, the emotions we feel and when. Rarely do we consciously decide what to feel. So, based on this knowledge, we can assume emotions are a completely reactive part of the human brain. Our emotions are simply neurons firing within our brain. Knowing this we should be able to stop our old behavior and change for the better, right? Yes, but here are the problems.
1. Addiction. When we feel an emotion our brain begins by rapidly producing various amino acids, called peptides. These peptides are released into the blood-stream and attach themselves to receptor sites that are designed for them throughout your body. These peptides are, in essence, drugs. And without them we really can experience withdrawals. These withdrawals usually come in the form of emotional outburst. These emotional withdrawals are really the throws of a dying nuronet trying to convince us that the old behavior we are trying to change or control is really the correct way to behave, and a lot of the time people relapse into old habits.
2. Repetition. Simply by feeling an emotion we are strengthening the neuronet that causes it and releasing the addictive peptides. The brain is a muscle, the more we use certain parts of it the better it gets at doing that function.
Let's just say that my problem emotion I'm currently working on is anger. Here I am hypothetically driving my hypothetical car down the road and some 70 year-old person is going 30 mp/h in a 60 mp/h zone. With no way to pass and a schedule to meet: I feel the anger, I get that body rush/high that the peptides create and may start yelling at the car in front of me. "Get off the road you old fart!" Time passes and that old fart finally turns right and is no longer on my mind. I've seemingly gotten over the whole situation. But then about 20 minutes later some super-sized women cuts me off because she was too focused on eating her bigmac and not driving. I get even more angry this time than I did with the old person and the peptides are released in an even larger dose. "Oh my god! Pay attention to the road you (explicit deleted)!" Now I may not realize it, but even if I feel bad later on, somewhere deep in my brain it's thinking "man that felt good." Thus, unfortunately, I'm more likely to repeat the behavior in the future.
Some external stimuli occurs and depending on how the brain has been wired we feel a given emotion. This is always the case be it a positive or negative emotion. Emotions are nothing but a reaction to our environment. Luckily, we do have the ability to change ourselves. All that is required is time, and to know yourself. The more you catch yourself feeling an undesired emotion and consciously make the decision to calm yourself down, the weaker the neuronet becomes. With constant practice the neuronet breaks apart and that emotion or behavior is no longer a part of your being. Many mystics and spiritual gurus of the past, Jesus, Buddha Siddhartha Gautama, amongst others have said "Know thyself." This requires that everyday we ask ourselves why we do the things we do, and upon figuring out our motives exercise our power to choose to decide whether it's something we want to continue to do or not.