There's an evolutionary reason why bad news sticks with us. It's called negativity bias, and it's the way we've evolved to identify threats to keep ourselves safe. But in a year of grim news, sometimes we all need reminding of the good things happening around the world too. Today on Hack, the local legends doing amazing things to help others, the rise of popular psychology, and happiness icon Dan Harris on how he overcame panic attacks, to be a more positive person.