This book, although full of scientific research results and psychological data, is very insightful about the nature of happiness. The author did a good job organizing research results and proposed practical ways to shift internal mindsets and external environments, the two big factors of happiness. The author listed the 9 factors of external happiness including the capacity to cause change (personal influence), variety, human interaction, money, and explained why some of these are too good of a good thing. For example having a lot of money would not bring more happiness than having sufficient amount of money. In conclusion, there is a delicate world of balance for happiness, as is anything else in our lives. You should try to have ADEQUATE levels of ALL good factors of happiness while being acceptive of external factors on the inside and reappraise things that happened to you.