I’ve been obsessed with happiness lately because few people seem to have it. It’s an important subject for leaders, entrepreneurs, business professionals and students because our thoughts control our behaviors. Neuroscientists and cognitive psychologists have found that negativity will derail our careers while a positive outlook will propel our success.

Mo Gawdat is also obsessed with happiness and has studied the topic more thoroughly than I have. Gawdat is a former engineer and Chief Business Officer of Google [X], the company’s radical innovation division. He had spent twelve years studying the science of happiness when his formula was put to the test. He lost his son, Ali, to a preventable medical error. Gawdat reveals the results of his research and his search for happiness in the book, Solve for Happy (recently released in paperback).

The book explained a lot of questions that I’ve had in my own pursuit of living a life of joy. I’ve spoken to the father of positive psychology, Dr. Martin Seligman. I’ve spoken to motivational leaders like Tony Robbins. I’ve spent time with joyful entrepreneurs like Richard Branson. I’ve talked to cognitive psychologists like Steven Pinker who believe we should be optimistic, grateful and happy for everything we have in our modern society.

Although I’m getting a lot better at putting myself into a state of happiness almost immediately, it’s taken years to reach that point. I’ve often wondered, why does it take work to stay positive? Gawdat explains that I’m not unusual—in fact, I’m perfectly normal.

“Worrying is the brain’s default position,” writes Gawdat. “Ample research has shown that we tend to think negative—self critical, pessimist, and fearful—thoughts more often than positive thoughts…Most of us tend to be negative most of the time.”

Our bias toward the negative is a mental holdover of our primitive brains. Negativity served an evolutionary purpose at one time, but acts more like a computer bug today. According to Gawdat, our brain is wired to look for threats. Its sole purpose is survival. If our ancestors were too optimistic, they wouldn’t have survived. The person who said— “There’s no tiger in the cave. Let’s go explore it”—didn’t live long. Our brain is programmed to find fault, seek out problems, criticize, judge, and complain. It doesn’t care if we’re engage in our work, fulfilled, joyful, and happy. Its purpose is to protect, not to encourage.

The problem, says Gawdat, is that our lives are made up almost entirely of positives. If we ignore the positives and focus on the negative—again, our default position—we make poorer decisions and lose out on the gains we might enjoy. Psychologists call it “negativity bias.” Simply put, a negative experience exerts a far stronger emotional toll on our psyche than a positive experience. It leads to “loss aversion,” which means we’d prefer to avoid a loss than acquire a gain.

Gawdat’s observation made me recall my own experience with thoughts and actions. As a senior in high school, a guidance counselor and several friends told me I’d never get into my top college choice: UCLA. I bought into the negativity bias and didn’t apply because I was avoiding a loss—rejection. As the application deadline drew near, my father, an Italian immigrant who had learned to look at the bright side, convinced me to give it a shot. “If you don’t get in, nothing will have changed. If you’re accepted, you’ll be happy.” he said.

I applied…and was rejected. My grades were okay, but not great. Then, something unexpected happened. I received a call from a professor who thought I had a unique blend of experience and talent for his program.

“Should I re-apply?” I asked.

“There’s no need to. I talked to the board. You’re already in,” he said. “See you in the fall.”

One conversation with my father changed my thoughts. My thoughts changed my actions. My actions changed my life. That’s the way positivity works.

According to Gawdat, we have the power to prolong our sadness, suffering, anxiety and worry. The good news—we also have the ability to “debug” the system. “Happiness depends entirely on how we control every thought,” says Gawdat. A positive, joyful and happy outlook is well within your grasp—if you put your mind to it.