“As a matter of self-preservation, one needs good friends or ardent enemies, for the former instruct one and the latter take one to task.”
That is attributed to Diogenes of Sinope, who was an ancient Greek wondering philosopher, although I'm not certain he relished the appellation.
Diogenes was a contemporary of Alexander the Great, but the two did not, apparently, like each other overmuch.
These articles generate some discussion or discourse, I hope. But, perhaps not.