There’s an elegant symmetry to traditional wedding vows: for better or for worse. But love is not symmetrical, and most of us don’t realize how lopsided it can be. The worse matters far more than the better in marriage or any other relationship. That’s how the brain works. Our thoughts and feelings are skewed by what researchers call the negativity effect, which is our tendency to respond more strongly to negative events and emotions than to positive ones. When we hear a mix of compl...