According to reports, some British investigation agencies have conducted a survey under the title "Who is the happiest in the world", and the statistics show that the top four are the following four types of people: writers who have just published novels; A woman with a child; a doctor who has just completed a major operation; a child who has successfully played with sand. What makes the above people happiest? ['Engage in creative labor and succeed with hard work.', 'Happiness lies in self-perception, not in material conditions.', 'Interest is the best teacher, happiness is in interest.', 'Anyone who has a purpose can succeed, and people who have a purpose can get happiness.']