“How can I be happy?”
Our brain creates happiness with just small changes in our daily lives!

It will bring you motivation and passion, joy and pleasure, and peace of mind.
The strength within me.
happy hormones

The brain has a structure that makes stress worse and hinders happiness.
These are ‘memory’ and ‘imagination’.
Especially when emotions are negative, you can easily fall into depression as various thoughts, such as regrets about the past or anxiety about the future, follow one another.
Moreover, these situations constantly cause stress and cause excessive secretion of cortisol, an anti-stress hormone, which has a negative impact on health.
If you're currently struggling with negative emotions like lethargy, anxiety, loneliness, or pain, stop thinking and get moving—whether it's taking a trip, eating something sweet, taking a walk in the sun, or taking a fragrant bubble bath.
Even these small changes cause our brains to secrete various hormones, which suppress negative emotions and create a sense of happiness.

The author of this book, Dr. Hajime Yamaguchi, a clinical psychologist and renowned expert in somatic psychology, focused on dopamine, oxytocin, serotonin, and endorphins, which play a major role in creating happiness, to the point of being called the "happiness hormones," among other hormones.
In this book, “Happiness Hormones,” he introduces the functions and roles of the four happiness hormones and says that anyone can easily create happiness hormones on their own through small changes in daily life.
There are many ways to do this, including exercise, a balanced diet, good posture, practicing gratitude, and improving interpersonal skills.

The four happiness hormones each play a different role in regulating the balance of our body and mind. So, when you feel lethargic in life, increase dopamine. If you are dissatisfied and stressed, increase oxytocin. If you feel anxious and nervous for no reason, increase serotonin. If you need physical and mental resilience, increase endorphins.
Are you in dire need of the happiness hormone right now? If so, I hope you'll find happiness in your daily life by consistently practicing the optimal happiness hormone habits introduced in this book.
Happiness is always within me.

First, I would like to say that what I want to convey through this book is not that kind of theory of happiness.
Because the moments of happiness are truly unique to each person, it is nearly impossible to generalize an individual's happiness.
Instead of such a theory of happiness, what if anyone could easily experience happiness through small changes in their daily lives? And if they could find that method, wouldn't that be the shortcut to happiness?
--- p.6

Dopamine, oxytocin, serotonin, and endorphins are often mentioned together, so they are often referred to by their initials, 'DOSE'.
It's also known by another nickname, the "success hormone." When DOSE is secreted, it not only creates a sense of happiness in the brain, but also has the following positive effects on our lives:

My mood becomes milder.
I feel full of energy.
You will have an optimistic mind.
The bond with people deepens.
Concentration increases.
Motivation arises.
Leadership skills become second nature.
I feel more confident at work.
--- p.20

Travel is the ultimate dopamine rush.
In particular, I recommend independent travel, where you decide on your own destination and freely plan how to get there.

If you're not sure where to go, consider a destination where you can experience something you enjoy, or where you can eat your favorite food.
And let's enjoy the process of getting there, whether by train, plane, or boat.

But remember, dopamine is released at its peak when you first achieve your goal.
Even if it's something you like, if you experience it twice, dopamine levels will decrease by half.
So, enjoy your 'first time' to the fullest.

--- p.78

In particular, it has been scientifically proven that lavender oil has a great effect in promoting oxytocin secretion.
Research continues to reveal the many positive effects of lavender scent interacting with oxytocin.
For example, it is said that if you smell lavender for 20 minutes, depression and anxiety are significantly reduced.
This also appears to be an effect that promotes oxytocin secretion.
As mentioned earlier, when oxytocin is secreted, serotonin neurons are also activated, increasing serotonin in the brain.
--- p.109

As mentioned earlier, serotonin is a neurotransmitter related to depression, and its deficiency can cause depression or anxiety.
But there's one interesting thing about the anti-gravity muscles and serotonin.
Stimulating the anti-gravity muscles causes serotonin to be secreted in return.
Animal experiments using rats have shown that applying electrical stimulation to the part of the brain involved in anti-gravity muscles causes serotonin neurons in the brain to fire.
This means that if you maintain good posture, the production of serotonin in the brain is promoted, which can help reduce depressed mood and provide mental stability.
Let's take a closer look at the research findings on anti-gravity muscles and depression.
New Zealand psychiatrist Wilkes divided 61 people diagnosed with mild to moderate depression into two groups: the 'sit as usual' group and the 'straight posture' group.
Randomly.
Afterwards, they were given stressful tasks, such as giving a speech in that position for five minutes or counting numbers.
Note that before the experiment, all participants were in a significantly forward-leaning posture.
The results of the experiment showed that participants in the 'straightening group' experienced increased positive emotions and spoke more words.
There has also been less groaning and worrying.
In particular, it has been found that a posture that opens the chest and keeps the angle of the shoulders horizontal helps reduce negative emotions such as anxiety.

--- p.136

When you lack serotonin, you start to feel mentally unstable and depressed.
Additionally, stress can cause you to become irritable and aggressive, a condition known as irritability.
Sometimes, we lose patience, become uncontrollable, or become unmotivated, leading to outbursts of anger or unreasonable behavior.
As already mentioned, serotonin suppresses anxiety, tension, anger, etc.
When the action of serotonin decreases, the ability to suppress emotions weakens, making it easier to get angry.
According to Masayoshi Konishi, a professor in the Department of Rehabilitation Medicine, people's serotonin secretion has been decreasing recently.
The cause lies in lifestyle habits.
This is understandable, as not only have we been liberated from the hard labor of the past and created a living environment with less physical strain (lack of exercise), but modern lifestyles have also changed significantly, including a reversed day-night lifestyle (lack of sunlight), irregular lifestyles due to stress, excessive work or smartphone use (lack of sleep), and nutritional deficiencies due to increased consumption of processed and instant foods.
It can be seen that there is a distance from serotonin secretion.
--- p.147

Especially when a person cries 'sobbing', he is not sending signals of sadness to others.
Crying is a way to relieve your own stress.
It's like a massage.
Sometimes I feel better when I get a massage that gently touches my skin.
This is because endorphins are released through light skin contact.
Likewise, the sensation of tears running down your cheeks has been shown to have the same effect as receiving a massage, possibly stimulating the release of endorphins.
Based on this fact, Field, an American touch care researcher, calls tears 'self-hugs.'

Additionally, physiological studies have shown that crying has a purifying effect on the mind.
So when you're stressed, if you cry a lot, your mind and body will relax and you'll be able to get back up again.

--- p.172

What about the type of exercise? To cut to the chase, if you exercise to increase your happiness, it doesn't matter whether it's aerobic or anaerobic.
However, aerobic exercise such as walking produces more endorphins.
Aerobic exercise also helps alleviate symptoms of depression, making it more effective for our goals.
A study by American psychiatrist Blumenthal found that 'continuing aerobic exercise for 16 weeks has a similar effect of alleviating symptoms as drug therapy of taking antidepressants for the same period, and also reduces the rate of relapse.'
This is because aerobic exercise also increases serotonin and dopamine.

--- p.221

Studies examining the relationship between happiness hormones and mindfulness have found that practicing mindfulness increases dopamine and serotonin.
When dopamine increases through mindfulness, concentration and flexibility of thought improve, and the mind enters a stable state due to the increase in serotonin.
In addition, melatonin, a metabolite of serotonin, increases, improving sleep quality.

Additionally, as serotonin increases, anti-stress hormones cortisol and norepinephrine decrease, reducing stress.
--- p.227

The way we work and the way we view our work have a huge impact on our happiness.
Here, we'll explore the relationship between the four happiness hormones and how we view work.

First of all, dopamine is secreted when you set a goal and try to achieve it.
From the perspective of 'work', it is secreted a lot, especially when you feel that what you are doing is enjoyable.

I seem to hear voices saying, 'It's ridiculous to say that work is fun.'

Even if it's not fun, think of a way to 'enjoy' it a little.
If it's monotonous and boring, set a goal and start by saying, "I'm going to do this much in an hour today." This will release dopamine to achieve the goal, and you'll feel motivated.

--- p.241