Eknath Easwaran's Commentary
According to this ancient saying, what is good in us and what is bad, our strong points and our weak points alike, develop because of constant association. When we associate with calm people, we become calm; when we associate with agitated people, we become agitated. When we frequent the company of people who are wise, we become wiser; when our company is otherwise, we become otherwise too.
We’ve all experienced this. When we have spent an evening with someone who is overwrought, we come home so agitated ourselves that we can’t get to sleep. But there is a positive side of the power of association: we absorb good qualities too, by spending time with people who embody them. Whenever we associate with people, we participate in their mental states.