The research on niceness cuts both ways: being agreeable is linked to a happier life and stronger relationships but also to lower pay and being exploited, and the self-erasing version of it predicts more distress, not less

The advice to be a nicer person assumes that niceness is a straightforward good, a dial you should turn up as far as it will go. In the research of Timothy Judge and colleagues, agreeableness was associated with higher life satisfaction, stronger social networks, more involvement in one’s community, and lower levels of stress. Analyzing surveys of around 10,000 workers over roughly two decades, they found that more agreeable people earned less, with the least agreeable men out-earning the most agreeable ones by about 18 percent. And niceness is not the same as goodness or kindness; a person can be pleasant and unkind, or blunt and deeply good. The nicest people, in the sense worth aspiring to, are not the most agreeable ones or the most self-sacrificing ones.