Once a cheater, always a cheater.
This myth comes from the idea that spouses who are inherently unfaithful commit all acts of infidelity and that people who cheat on their spouses do so by premeditation only. It may feel that way at first, but many unfaithful partners are ashamed of themselves and what they have done.
For most, betrayal is an act that they never expected to commit. The fact that they did betray can leave the offenders confused and humiliated. Often, the guilty parties are glad to be discovered, knowing that they no longer have to hide what they did.
The affair is more often a symptom of dissatisfaction within a marriage. One spouse feels distanced and unattended, leading to an acceptance of affections outside the marriage structure.
Honesty is the key, and once the problems that led to the affair are resolved, the need to look outside of the marriage is eliminated.