Principle: As behavioral economists like to point out, we become irrational when we're losing. One landmark study suggests losses hurt twice as much as gains satisfy, all of which means humans try to avoid losing at all costs.
Payoff: Loss aversion is what makes couples stay up and fight all night, refuse to compromise or apologize, and not recognize the good things in front of them because they're too focused on how things used to be. "Whenever we feel like losing something, we act rashly," says Ms. Szuchman. "I still like to be right, but I do try a lot more to call a timeout when I know that I just keep saying the same thing or when I know I just don't want to lose."
Kids and the changes they bring can kick-start a couple’s loss aversion, too, adds Szuchman. Instead of looking back fondly on the “good times,” and measuring everything against those carefree days in your 20s, reframe, consider what you’ve gained, and establish a new status quo.