You get the resolve that allows you to stand up and move ahead. So, it actually strengthens the sense of togetherness at a time when you're being ripped apart because of personal pain. Most people believe that monogamy is the norm, and that most people are monogamous. These beliefs are not true, They are a myth. So when infidelity is exposed, most people make a judgement and believe in punishment for the perpetrator, as if they're unusual when, in fact, they're not.
People like to debate whether monogamy is natural.
From my personal experience in life and as a counselor for over 16 years, it is not. It's not that couples set out at the beginning of their marriage planning to be unfaithful - they have strong intentions to be monogamous. It's just that in our sex-saturated society, the deck is stacked against us. It's an uphill battle to remain faithful. The glorification of affairs and the use of sex to sell undermine monogamy.