In a nutshell, mindfulness is the ability to recognize what is happening in your mind right now—anger, jealousy, sadness, the pain of a stubbed toe, whatever—without getting carried away by it.
10% Happier
Harris' book, 10% Happier: How I Tamed the Voice in My Head, Reduced Stress Without Losing My Edge, and Found Self-Help That Really Works – a True Story, was published in March 2014.