安分守己
Know one's distance.
Know where to draw a line.
Mind one's own business.

eg：John knows his distance and never puts his finger in other person's pie.

中英俚语俗语来源：苏轼诗：“胡不安其份，但听物所诱。”

同义词：循规蹈矩 Walk the chalk.
反义词：横行无忌 Throw one's weight about.