The Princess of Wales has a suggestion to parents: Please put down the phone.

In a 2016 study, a positive outlook was associated with longer life for nearly 4,000 older French men and women studied over 22 years. The unprecedented study has allowed researchers to get closer to determining the main characteristics of a happy life. "The clearest message that we get from this 75-year study is this: Good relationships keep us happier and healthier. There are a lot of reasons why a positive outlook might improve your physical health and help you live longer. Optimists also have better health habits.