Men have little control over whether or not their women step out on them - it's their grasp of the state of the relationship, and not the reality, that motivates them. Your qualities as a partner - as a lover - are immaterial. If a women decides that her relationship is less than complete, she'll start scouting about to find someone with whom she can have that perfect relationship. Because she's already determined that the reason for her cheating is something you've neglected to do, she'll easily be able to blame her cheating on you.
"Emotional distance" is the term applied to the first of these causes. Women have a desire for emotional engagement. They want to feel loved and they want their man to pay attention to them. What do women want? It's a question that's been asked for centuries, and whatever answers have been given always seem to fall short. In a relationship, a woman wants to have her sense of worth fortified by her man. If, at the end of the day, she doesn't feel that sense of worth, she'll blame her man no matter what he's really done. realreason|The actual cause notwithstanding], when the emotional distance between a man and a woman grows, she's likely to start shopping around.
The second reason women will cheat on their men is neglect. That's reasonable, but it's still fraught with pitfalls. The man who's always underfoot, always in his woman's face, will before long be considered to be clingy: too dependent, too needy, too immature - and too replaceable. She'll feel claustrophobic. On the other hand, however, when a man understands that he's got to give his woman time on her own to grow, and enhance those things he loves about her, she might decide he doesn't really care. She might decide he's neglecting her, and she'll use that space to find another man.
Most women place great importance on their appearance. Right or wrong, it's the source of much of their self-esteem, and a man who neglects to compliment her on her beauty, particularly after she's spent much time on it, is a man who's risking his woman stepping out on him. Her self-esteem will be get the reinforcement it needs from another man, she'll think, because she feels she's no longer getting that in her relationship - no matter what her man's actually doing. If a woman isn't feeling good about herself, no matter what you've done to boost her self-esteem, there's a good chance she'll decide your efforts are inadequate and start looking for someone who can make her feel better about herself.
Finally, a woman is likely to cheat on her man if she simply feels bored and needs a change of scene. The woman who does this is particularly immature, because she needs the uninterrupted sense of being in a relationship as opposed to being on her own, strong, independent and in charge of her own life. A woman who stays in a relationship for the emotional (and financial) security, rather than honestly ending it and establishing herself as a single woman on her own, isn't going to solve any problems by darting from one relationship to another.
Regardless of the reason a woman gives for cheating on her man, the awkward truth is that they probably weren't suited to each other. True love requires honesty and communication, and a woman who cheats on her man destroys any trust there may have been. If a woman can't tell you that her needs aren't being met, as we talked about above, then she's likely not the right woman for you to be thinking about spending the rest of your life with.