There are many reasons why relationships fail, but if you look at what drives the deterioration of many relationships, it’s often a breakdown of kindness. As the normal stresses of a life together pile up—with children, career, friend, in-laws, and other distractions crowding out the time for romance and intimacy—couples may put less effort into their relationship and let the petty grievances they hold against one another tear them apart. In most marriages, levels of satisfaction drop dramatically within the first few years together. But among couples who not only endure, but live happily together for years and years, the spirit of kindness and generosity guides them forward.
Emily Esfahani Smith writing in The Atlantic