Life should be getting easier, but it's not. It's a paradox of the modern world. At the very moment that science and technology are providing us previously unimagined longevity, health, and social interaction, too many of us struggle to live meaningful, peaceful lives full of love and contribution.

There is no question that we've made incredible progress over the last fifty years. That computer in your pocket called your phone is 120 million times more powerful than the guidance computer for Apollo 11-the first rocket to land people on the moon. Progress in health technology has been similar. Leukemia killed 86 percent of the children who contracted it fifty years ago-now it kills less than half that. In the last twenty-five years, child mortality, maternal mortality, and deaths from malaria all declined 40 to 50 percent. If physical health and safety were the issue and you could pick only the moment to be born in the world but not to whom, you could not do better than to choose today.

Behavioral science is another matter. Yes, we are living longer. But it is hard to make the case that we are living happier, more successful lives.

We have more accurate information than ever about illnesses that are largely due to lifestyle. Yet despite billions of dollars spent on research, our healthcare systems are staggering under the dramatically rising rates of obesity, diabetes, and chronic pain. Mental illness is rapidly becoming much more of a problem, not less. In 1990, depression was the fourth leading cause of disability and disease worldwide after respiratory infections, diarrheal illnesses, and prenatal conditions. In 2000, it was the third leading cause. By 2010, it ranked second. In 2017 the World Health Organization (WHO) rated it number one. Approximately forty million Americans over age eighteen have been diagnosed as having an anxiety disorder, and almost 10 percent of Americans report "frequent mental distress." We don't feel as though we have adequate time. We don't take care of ourselves the way we'd like. Our health suffers. Many of us are putting one foot in front of the other while lacking a real sense of purpose and vitality. Every day, someone who seems to have a good life decides to eat a bottle of pills rather than continue one more day.

How can this be?

I believe it is because we have not risen to the challenges of being human in the modern world. Some of the very things we have been doing over the last hundred years to foster human prosperity have created our conundrum. Take the case of innovations in technology. Each step forward-radio to TV to the Internet to the smartphone-has created greater mental and social challenges, and our culture and minds haven't adjusted rapidly enough in effective and empowering ways.

As a result of our technology, we are all exposed to a constant diet of horror, drama, and judgment. In addition, many of us are left feeling overwhelmed and threatened by the rapid pace of change. A concrete example: only a few decades ago children ran and played freely in ways that could bring child endangerment complaints today. This increased protectiveness is not due to the world actually becoming more dangerous; research suggests it has not. Our impression that the world is less safe results more from exposure to uncommon events through the media. No matter how calm we feel, we can turn on our computers and see a tragedy unfold, complete with images of those who died just minutes ago. The twenty-four-hour news cycle shreds our veil of safety with constant videos of capricious violence.

When the external world changes at this speed, our internal world needs to change too. That sounds logical, but it is hard to know what steps to take.

The good news is that behavioral science has developed a plausible answer to how we can do better. Over the last thirty-five years, my colleagues and I have studied a small set of skills that say more about how human lives will unfold than any other single set of mental and behavioral processes previously known to science. That is not an exaggeration. In over one thousand studies, we've found that these skills help determine why some people thrive after life challenges and some don't, or why some people experience many positive emotions (joy, gratitude, compassion, curiosity) and others very few. They predict who is going to develop a mental health problem such as anxiety, depression, trauma, or substance abuse, and how severe or long-lasting the problem will be. These skills predict who will be effective at work, who will have healthy relationships, who will succeed in dieting or exercise, who will rise to the challenges of physical disease, how people will do in athletic competition, and how they will perform in many other areas of human endeavor.

This set of skills combines to give us psychological flexibility. Psychological flexibility is the ability to feel and think with openness, to attend voluntarily to your experience of the present moment, and to move your life in directions that are important to you, building habits that allow you to live life in accordance with your values and aspirations. It's about learning not to turn away from what is painful, instead turning toward your suffering in order to live a life full of meaning and purpose.

Wait, turning toward your suffering?

That's right. Psychological flexibility allows us to turn toward our discomfort and disquiet in a way that is open, curious, and kind. It's about looking in a nonjudgmental and compassionate way at the places in ourselves and in our lives where we hurt, because the things that have the power to cause us the most pain are often the things we care about most deeply. Our deepest yearnings and most powerful motivations lie hidden inside our most unhealthy defense systems. Our impulse is usually either to try to deny our pain, by suppression or self-medication, or to get caught up in dwelling on it through rumination and worry, allowing it to take charge of our lives. Psychological flexibility empowers us to accept our pain and live life as we desire, with our pain when there is pain.

I believe psychological flexibility is a means of achieving human liberation; it is the counterweight that people need to rise to the increasing challenges of the modern world. And hundreds of studies show that the skills that allow us to develop psychological flexibility can be learned, to a degree even through books such as this one. I know these are big claims, but if I do my job, by the end of this book you will understand why the skills that build flexibility are so powerful and how you can begin developing them in yourself.

It's perhaps not surprising that the core message of turning toward our pain echoes other approaches, such as the mindfulness literature developed out of spiritual traditions, or the emphasis on exposure in cognitive behavioral therapy. But the new science of psychological flexibility is not aping old themes-by repeatedly asking why these methods work, it has arrived at a deeper understanding of the importance of flexibility skills and how to establish them. This understanding was produced by a scientific community that followed a new path of research, resulting in a new and more integrated set of methods for living happier and healthier lives.