“Nature gave us friendship,” Cicero wrote, “as an aid to virtue, not as a companion to vice.”What he meant was that friends are supposed to make you better, not make you worse. Friends are supposed to reinforce your good habits, not encourage your bad ones.It was Marcus Aurelius who said that we take the shape of the thoughts we have most often. He would probably agree to an extension of that logic: We are formed into the shape of the role we play in our circle of friends. We become like the people we spend the most time with.Do the people you spend your time with make you better by association or worse? Do you make the people around you better as well? The question for you today, then, is whether you and your friends pass that test.