These days, nobody's social circle is without someone who's gotten, getting, or about to get a divorce. A couple I know is in the middle of a divorce.
All indications point to the prior existence of a hidden affair.
In this situation, our hearts go out to the partner who remains monogamous. Overwhelmed by a potent mixture of anger, guilt, and wounded narcissism, they're often kept afloat by the solace and support of caring friends. The faithful spouse is perceived as the more disadvantaged, almost without fail. After all, the other partner is now comfortably ensconced in a new relationship. As a sex and marital therapist, I've seen lots of marriages dissolve in this pattern, and it has changed how I focus my efforts to help both partners.