In The Upside of Your Dark Side, two pioneering researchers in the field of psychology show that while mindfulness, kindness, and positivity can take us far, they cannot take us all the way. Emotions such as anger, anxiety, guilt, and sadness might feel uncomfortable, but can also be useful.

For instance anger fuels creativity, selfishness increases courage and self-doubt enhances performance.  The key lies in what the authors call “emotional, social, and mental agility,” the ability to access our entire psychological toolkit—not just the “good” ones—which allows us to climb the highest peaks and handle the deepest valleys.