"Hurt people, hurt people."
Roger Greenberg (Ben Stiller) is a former-musician come carpenter who's just been released from a mental hospital and is house sitting for his brother in Los Angeles. The often abrasive, anti-social Greenberg meets his match in Florence (Greta Gerwig), his brother's sweet assistant who, despite her sunny demeanor, has issues of her own. This quote comes from a self-help book Greenberg reads and the line is repeated by Florence, as if to emphasize that the hell we put the people we love through is often involuntary.
Oscar-worthy tip: When someone is hurtful, recognize they're going through their own pain. We only hurt the one's we love…