Stop listening to the excuses of your ex or current partner, if they even acknowledged to cheating, and find out the real reasons. Sometimes the reasons get very abstract and deep, influenced by how the cheater saw relationships as a child. Even if a cheater confesses, it may be difficult to understand why they did it. This article should provide some insight on reasons why people cheat in relationships.
1. Unhappiness + Lack of Communication
Chances are, you were completely thrown off guard when you found out your partner cheated because everything seemed to be going along fine. In actuality, your partner was unhappy with the relationship in some way and failed to communicate that to you. Originally, the cheating may not have been intentional, but they found what you lacked in another person. This is one of the most common reasons why people cheat in relationships.
This sums up all the "scumbag" reasons why people cheat in relationships. Your partner is proposed by an attractive person, or just someone who gives them attention. They may think of you only for a moment, if at all, but their main focus is the chance to "score" with the person right in front of them.
3. Honest Mistake
I believe this is the rarest of reasons why people cheat in relationships. Sometimes good people make horrible mistakes that cause a lot of hurt to the ones they love. This requires a serious lapse in judgment in order for it to be the true reason. Many cheaters will claim this reason, when it's actually number one or two.