The father of Positive Psychology Martin Seligman theorized that while 60 percent of happiness is determined by our genes and the environment, the remaining 40 per cent depends on us. Born again and get new genes is impossible, you can instead work on that 40%. How? The science suggests at least 8 streets.

1. Spending (at least) 20 minutes per day outdoors.
2. Strive to be happy.
In two studies published in the Journal of Positive Psychology they have confirmed that when people actively seek to be happy, improve their mood, feeling happier at the end of those who do not.
3. Find out your best features, and strive to use them.
4. Exercise regularly.
5. Give a meaning to life.
Researchers at Tohoku University in Japan have produced a seven-year study of more than 43,000 adults aged 40 to 79 years, asking them if they had ikigai (a Japanese term that means "meaning of life"), and then monitored their health state. 95 percent of respondents who reported having given meaning to his life were alive seven years after the initial investigation against approximately 83 per cent of those who had not reported any reason to live. The lack of ikigai, according to the researchers, would be particularly associated with death due to cardiovascular disease.
6. Spend time with people happy ... or with their friends
Happiness is contagious
7. Cultivate strong social relationships.
8. Taking care of others.

From Focus (ita)