When two friends part they should lock up each other's secrets and exchange keys. The truly noble mind has no resentments. — Diogenes. 4th-century BC Greek Cynic philosopher
As a matter of self-preservation, a man needs good friends or ardent enemies, for the former instruct him and the latter take him to task.
Discourse on virtue and they pass by in droves. Whistle and dance the shimmy, and you've got an audience.