What IS happiness, really? And what's the difference between biting into a bar of chocolate and a much more sustained contentment that often eludes us?

Ph.D. psychologist Emma Seppälä has studied happiness for much of her career. She's a best-selling author who also teaches business leaders at the Yale School of Management.

Turns out, achieving career success and wealth doesn't lead to that contentment. If you're searching for mental well-being, Emma says: Start with your body, specifically, your breathing.

She explains how anyone, from a stressed out manager to a soldier in a warzone, can use breathing techniques to gain focus and ingenuity. Emma also deconstructs many myths about what makes us happy, and how focusing our minds on others leads to long-term emotional resilience.