I was delighted to interview a friend of mine, Nancy Davis Kho. She is the author of a fabulous book called The Thank You Project, where she describes how, in her 50th year, she decided to write 50 thank you letters. It is a really interesting book and Nancy is a really interesting person to interview. She talks not only about how amazing it was to write the letters and how it changed her life in lots of ways, but also some of science behind why gratitude is such a powerful tool.