While not downplaying the power of unconscious motivation, Petito's murder, which is not unusual for abused women, might have been avoided had she followed one simple rule: to better know your partner before becoming intimate.
Nearly a hundred-years ago, an unmarried American psychiatrist underwent his training analysis with Freud in Vienna. This then lasted six months and, at their last meeting, Freud expressed the wish that the doctor be lucky enough to gain a happy marriage. "With all your psychological knowledge can luck be a factor?" the surprised doctor asked. "Of course, because one cannot know someone without living with them for a long time."
Thus Freud's good advice for all: It takes a long time to know someone. Take it.