I dedicate some time to re-read the book of Marci Shimoff Happy for No Reason: 7 Steps for Being Happy from the Inside Out. She refers to the research of Lykken and his team who have been studying in the 1980s thousands of twins, including a number of identical twins who were raised apart. What they discovered is that those twins had a similar genetic happiness set-point that was true for them in 50 percent. The rest 50 percent was influenced by other circumstances. It means that if your family is grumpy, you have a big change to inherit that!
This would also explain why people who won the lottery after 2 years came back to their previous level of happiness became suicidal again. And also why people after a big tragedy in their life could become cheerful and good jokers again. This is how the happiness set-point works. Probably you know it from your own experience that those of your acquaintances who were very optimistic and happy in the high-school most of the time stay the same even after 30, 40 ,50 years. And those who were always with a sad face or complaining are still complaining in the same way.
Is that our destiny to be grumpy or happy most of the time? Actually not, there is a hope. Studies of Sonja Lyubomirsky, Kennon Sheldon, and David Schaade confirmed findings of Lykken but added something new. Again 50 percent of our happiness comes from the genetics but from the remaining 50 percent, only 10 percent is created by our circumstances such as career, marital status, and wealth. The rest 40 percent depends completing of us! This 40 percent is determined by our habitual thoughts, feelings, words, and actions, in other words on your mindset. And this is something you can work on and boost your level of happiness!