text: This is a complex question with no one simple answer. But it general it comes down to boundaries. For some people, infidelity is a strong boundary that they will not tolerate being violated. It can also shatter trust beyond repair. But other people are willing to give their partner a chance to earn back their trust. Still others stay married for religious or financial reasons, and some have self-esteem issues and don't believe they are worthy of a partner who doesn't cheat on them. There are more possibilities, but these are a few of the common ones.\nDr. Barb Nefer, www.bnlifeskills.com