“According to current research, in the determination of a person’s level of happiness, genetics account for 50 percent; life circumstances, such as age, gender, ethnicity, marital status, income, health, occupation, and religious affiliation, account for about 10 to 20 percent; and the remainder is a product of how a person thinks and acts. In other words, people have an inborn disposition that’s set within a certain range, but they can boost themselves to the top of their happiness range or push themselves down to the bottom of their happiness range by their actions. This finding confirmed my own observations. It seems obvious that some people are more naturally ebullient or melancholic than others and that, at the same time, people’s decisions about how to live their lives also affect their happiness.”(Gretchen Rubin, The Happiness Project.)