According to the book “Discovering Psychology” by Don Hockenbury and Sandra E. Hockenbury, an emotion is a complex psychological state that involves three distinct components: a subjective experience, a physiological response, and a behavioral or expressive response.

In addition to trying to define what emotions are, researchers have also tried to identify and classify the different types of emotions. The descriptions and insights have changed over time:

a. In 1972, psychologist Paul Eckman suggested that there are six basic emotions that are universal throughout human cultures: fear, disgust, anger, surprise, happiness, and sadness.
b. In the 1980s, Robert Plutchik introduced another emotion classification system known as the “wheel of emotions.” This model demonstrated how different emotions can be combined or mixed together, much the way an artist mixes primary colors to create other colors.
c. In 1999, Eckman expanded his list to include a number of other basic emotions, including embarrassment, excitement, contempt, shame, pride, satisfaction, and amusement.
Plutchik proposed eight primary emotional dimensions: happiness vs. sadness, anger vs. fear, trust vs. disgust, and surprise vs. anticipation. These emotions can then be combined to create others (such as happiness + anticipation = excitement).

Key Elements of Emotions
In order to better understand what emotions are, let’s focus on their three key elements, known as the subjective experience, the physiological response, and the behavioral response.

The Subjective Experience
While experts believe that there are a number of basic universal emotions that are experienced by people all over the world regardless of background or culture, researchers also believe that experiencing emotion can be highly subjective. Consider anger, for example. Is all anger the same? Your own experience might range from mild annoyance to blinding rage. While we have broad labels for emotions such as “angry,” “sad,” or “happy,” your own experience of these emotions may be much more multi-dimensional, hence subjective. We also don’t always experience pure forms of each emotion. Mixed emotions over different events or situations in our lives are common. When faced with starting a new job, you might feel both excited and nervous. Getting married or having a child might be marked by a wide variety of emotions ranging from joy to anxiety. These emotions might occur simultaneously, or you might feel them one after another.

The Physiological Response
If you’ve ever felt your stomach lurch from anxiety or your heart palpate with fear, then you realize that emotions also cause strong physiological reactions. (Or, as in the Cannon-Bard theory of emotion, we feel emotions and experience physiological reactions simultaneously.) Many of the physiological responses you experience during an emotion, such as sweaty palms or a racing heartbeat, are regulated by the sympathetic nervous system, a branch of the autonomic nervous system.

The autonomic nervous system controls involuntary body responses, such as blood flow and digestion. The sympathetic nervous system is charged with controlling the body’s fight-or-flight reactions. When facing a threat, these responses automatically prepare your body to flee from danger or face the threat head-on. While early studies of the physiology of emotion tended to focus on these autonomic responses, more recent research has targeted the brain’s role in emotions. Brain scans have shown that the amygdala, part of the limbic system, plays an important role in emotion and fear in particular.

The amygdala itself is a tiny, almond-shaped structure that has been linked to motivational states such as hunger and thirst as well as memory and emotion. Researchers have used brain imaging to show that when people are shown threatening images, the amygdala becomes activated. Damage to the amygdala has also been shown to impair the fear response.

The Behavioral Response
The final component is perhaps one that you are most familiar with—the actual expression of emotion. We spend a significant amount of time interpreting the emotional expressions of the people around us. Our ability to accurately understand these expressions is tied to what psychologists call emotional intelligence, and these expressions play a major part in our overall body language.

Research suggests that many expressions are universal, such as a smile to indicate happiness or a frown to indicate sadness. Sociocultural norms also play a role in how we express and interpret emotions. In Japan, for example, people tend to mask displays of fear or disgust when an authority figure is present. Similarly, Western cultures like the United States are more likely to express negative emotions both alone and in the presence of others, while eastern cultures like Japan are more likely to do so while alone.

Emotions vs. Moods
In everyday language, people often use the terms “emotions” and “moods” interchangeably, but psychologists actually make distinctions between the two. How do they differ? An emotion is normally quite short-lived, but intense. Emotions are also likely to have a definite and identifiable cause.

For example, after disagreeing with a friend over politics, you might feel angry for a short period of time. A mood, on the other hand, is usually much milder than an emotion, but longer-lasting. In many cases, it can be difficult to identify the specific cause of a mood. For example, you might find yourself feeling gloomy for several days without any clear, identifiable reason.

The ultimate productivity hack is saying no. Not doing something will always be faster than doing it. This statement reminds me of the old computer programming saying, “Remember that there is no code faster than no code.” The same philosophy applies in other areas of life. For example, there is no meeting that goes faster than not having a meeting at all. This is not to say you should never attend another meeting, but the truth is that we say yes to many things we don’t actually want to do. There are many meetings held that don’t need to be held. There is a lot of code written that could be deleted. How often do people ask you to do something and you just reply, “Sure thing.” Three days later, you’re overwhelmed by how much is on your to-do list. We become frustrated by our obligations even though we were the ones who said yes to them in the first place. It’s worth asking if things are necessary. Many of them are not, and a simple “no” will be more productive than whatever work the most efficient person can muster.

Why we say Yes?

We agree to many requests not because we want to do them, but because we don’t want to be seen as rude, arrogant, or unhelpful. Often, you have to consider saying no to someone you will interact with again in the future—your co-worker, your spouse, your family and friends. Saying no to these people can be particularly difficult because we like them and want to support them. Collaborating with others is an important element of life. Do whatever favors you can, and be warm-hearted and direct when you have to say no. But even after we have accounted for these social considerations, many of us still seem to do a poor job of managing the tradeoff between yes and no. We find ourselves over-committed to things that don’t meaningfully improve or support those around us, and certainly don’t improve our own lives. Perhaps one issue is how we think about the meaning of yes and no.

Difference between Yes and No

The words “yes” and “no” get used in comparison to each other so often that it feels like they carry equal weight in conversation. In reality, they are not just opposite in meaning, but of entirely different magnitudes in commitment. When you say no, you are only saying no to one option. When you say yes, you are saying no to every other option. I like how the economist Tim Harford put it, “Every time we say yes to a request, we are also saying no to anything else we might accomplish with the time.” Once you have committed to something, you have already decided how that future block of time will be spent. In other words, saying no saves you time in the future. Saying yes costs you time in the future. You have to pay back your commitment at some point. No is a decision. Yes is a responsibility.

Saying No

Saying no is an important skill to develop at any stage of your career because it retains the most important asset in life: your time. As the investor Pedro Sorrentino put it, “If you don’t guard your time, people will steal it from you.” You need to say no to whatever isn’t leading you toward your goals. You need to say no to distractions. Nobody embodied this idea better than Steve Jobs, who said, “People think focus means saying yes to the thing you’ve got to focus on. But that’s not what it means at all. It means saying no to the hundred other good ideas that there are. You have to pick carefully.” There is an important balance to strike here. Saying no doesn’t mean you’ll never do anything interesting or innovative or spontaneous. It just means that you say yes in a focused way. Once you have knocked out the distractions, it can make sense to say yes to any opportunity that could potentially move you in the right direction.

Upgrading Your No

Over time, as you continue to improve and succeed, your strategy needs to change. The opportunity cost of your time increases as you become more successful. At first, you just eliminate the obvious distractions and explore the rest. As your skills improve and you learn to separate what works from what doesn’t, you have to continually increase your threshold for saying yes. You still need to say no to distractions, but you also need to learn to say no to opportunities that were previously good uses of time, so you can make space for great uses of time. It’s a good problem to have, but it can be a tough skill to master. In other words, you have to upgrade your “no’s” over time. Upgrading your no doesn’t mean you’ll never say yes. It just means you default to saying no and only say yes when it really makes sense. The general trend seems to be something like this: If you can learn to say no to bad distractions, then eventually you’ll earn the right to say no to good opportunities.

How to say No

Most of us are probably too quick to say yes and too slow to say no. It’s worth asking yourself where you fall on that spectrum. If you have trouble saying no, you may find the following strategy proposed by Tim Harford, the British economist. He writes, “One trick is to ask, “If I had to do this today, would I agree to it?” It’s not a bad rule of thumb, since any future commitment, no matter how far away it might be, will eventually become an imminent problem.” If an opportunity is exciting enough to drop whatever you’re doing right now, then it’s a yes. If it’s not, then perhaps you should think twice. This is similar to the well-known “Hell Yeah or No” method from Derek Sivers. If someone asks you to do something and your first reaction is “Hell Yeah!”, then do it. If it doesn’t excite you, then say no. It’s impossible to remember to ask yourself these questions each time you face a decision, but it’s still a useful exercise to revisit from time to time. Saying no can be difficult, but it is often easier than the alternative. What is true about health is also true about productivity: an ounce of prevention is worth a pound of cure.