don't shit in your own nest

rude slang Do not engage in troublesome or dubious behavior at one's home, place of business, or any location where one frequents, for it invites undesired consequences. I told him, "Don't shit in your own nest." But he still insisted on having an affair with his secretary, and now the scandal is ruining both his career and his personal life. A: "I don't want to date any of the guys in my school—I mean, it would be so awkward to have to see them all the time if we broke up!" B: "So you're someone who believes in 'don't shit in your own nest,' huh?" Please don't get into a relationship with anyone at your new job, OK? Don't shit in your own nest.