Not everyone works in a positive environment. Salespeople can go for days dealing with one unhappy, angry, or dissatisfied customer after another. They can experience bouts of rejection that last for weeks. But it's possible to maintain a happy mind-set, despite being surrounded by negative circumstances. According to the author of "The Happiness Advantage," only 10 percent of happiness depends on our external world. The other 90 percent depends on how our brain processes the world. So instead of focusing on the problems, mistakes, and dangers that might surround you, make a positive choice to look at and be grateful for the good things in your life.