Jeffrey Eugenides said this quote

There’s a thing they’ve figured out about love. Scientifically. They’ve done studies to find out what keeps couples together. Do you know what it is? It isn’t getting along. Isn’t having money, or children, or a similar outlook on life. It’s just checking in with each other. Doing little kindnesses for each other. At breakfast, you pass the jam. Or, on a trip to New York City, you hold hands for a second in a smelly subway elevator. You ask “How was your day?” and pretend to care. Stuff like that really works.