If you can't trust someone, you can't be in a relationship with them. If they broke your trust once and cheated, most likely they will again. They cheated for a reason, because they don't really love you, or they can't love you. And if they can't, then why stay together?
Trust is the number one ingredient to having a good relationship. Once a person has broken your trust by cheating, it is almost impossible to stay with them. Some people do, but overall it is foolish to do so, because how can you trust them?
Somethings though, we simply Think we can't trust a person because another guy or girl hurt us. Then if the person you are with does the slightest thing that reminds you of the other person, you don't trust them. But not all men are the same. Not all women are the same. Just because one man or one woman broke your trust by cheating, that doesn't mean all people of the opposite sex will cheat on you.
It can be hard to trust another person after you have been badly hurt by someone. Our heart tends to close up and we put walls up to keep everyone else out. But then you are all alone, and that is sad.
I think the secondary issue when we are cheated on is we lose faith in ourselves. We think, "Well if I caused that other person to cheat on me, then will I cause this next person to cheat one me too?" But some people are just scoundrels. It doesn't matter what you do or how well you love them, they will still cheat. That is because the issue is with them, not you.
With other people, it doesn't matter how much you hurt them or "neglect" them, they will never cheat on you, because they are a good person. They were raised right. They had good models in their parents. They fear God. They have a strong inner desire to do the right thing, not because you necessarily deserve it, but because they simply desire to do the right thing. They treat you right, because they know they answer to God.
It could be said that all people "deserve" to be cheated on at some point. We all mess up and say stupid stuff and do things that deserve cheating. But still, it is wrong.
Cheaters love to blame the victim. They rationalize their cheating in their head and say that the other person caused it. But in a relationship, it should not be about what a person deserves, it is about doing the right thing. Some people do not care at all about doing the right thing, and that is why they cheat.
You may have caused the cheating in little ways, by not being perfectly nice to the person etc., but you still did not deserve to be cheated on. You deserve to be with someone who won't cheat on you. That is what you deserve.
People often stay with a cheater because they think that is all they deserve. They blame themselves. They think, "Well if I would have given them more sex they wouldn't have cheated" or "If I would have been nicer to them...etc." It is good to evaluate yourself a little bit. Why were they not happy with you? What Did you do? But ultimately they were the one at fault, because they did the wrong thing. Even if you did deprive them of sex, they still should not have cheated. Even if you weren't perfectly nice to them, they still should not have cheated.
The main issue with a cheater is that they have no fear of God.
What makes or breaks a person is the degree to which they fear God and want to honor God with their lifestyle. Their faithfulness should not be contingent on what you do. It is easy to blame yourself when someone cheats. You think, "Maybe I was working too much. Maybe I didn't look hot enough. Maybe I was not kind enough." But the problem was mainly with them and not you. They do not fear God enough. They do not Listen to God. They have issues and cannot be faithful to anyone, because they don't respect anyone, because they don't respect God. If you don't respect God, you will not respect anyone. If you can't respect yourself, you can't respect anyone else.
Cheating is an issue of respect. So many men do not respect women at all, so they have no problem cheating on their woman. So many women do not respect men, so they think their man deserves to be cheated on. Granted your significant other may have acted in a way that caused you to not respect them, but cheating is still wrong.
People also cheat when they are not satisfied with their person. If you are not happy with the person you are with, because you are too spoiled and can't be content with them, then move on to the next person. It is a simple as that. Maybe they don't have the body type that you want. Maybe there is some addiction they have that bothers you. Maybe they are addicted to drugs. There can be legitimate and good reasons why you are not all that attracted to them. Maybe they are verbally or physically abusive. If that is the case, just move on to another person, but don't sleep with two people at a time. That is messed up.
Another big reason for cheating is that the person doesn't want to be alone. If they break up with the person they are with, they will have to be alone for awhile. They don't want to leave the relationship they are in until they for sure have another relationship, because they are unable to just be alone with themselves, because they hate themselves. So they are testing the waters with other people to see if they can find something better.
It does seem to be a fact of life that most people are only with someone until someone better comes along. Most people think the grass is greener on the other side. How can you prevent this problem? You need to initially find someone that you can be totally satisfied with. But so many people settle. They think, "Well this person is good enough." Simply because they don't want to be alone, so they get with someone, but that is not really the kind of person that they want. And so they are with them, but not happy, and kind of hoping that someone better will come along. If you are not satisfied with the person you are with, then don't be with them. Or you could just get over yourself and your picky perfectionism and decide to love them anyways.
No one is perfect. You will not find a perfect person. We all have flaws. No one is going to be Everything that you want. I think God allows this to happen so that we will not idolize anyone. You have to find that perfect middle ground. Be satisfied with the person you are with, but don't idolize them. The only perfect being is God. He is the only entity who is everything that you want and need. When you try to find someone who is a god, you will always end up dissatisfied, because no one is a god. No human being is perfect like God. So give up the search. Either be alone forever, because you refuse to be satisfied with anyone, or give up your perfectionism and find someone that you can be mostly happy with, and then Stay with them. "What God has joined together let no one separate" unless they cheat on you.
God loves you! May God bless you and give you wisdom in your relationships. :)