Ever been cheated on? Hell ya. Does it suck? So much.
But stop blaming yourself, you could have done nothing to stop it. Science says, that it is inevitable. A person's genetics, hormonal and social factors play a pivotal role in determining if that person is likely to cheat or not. So maybe, once a cheater always a cheater has some scientific basis after all.
Well, science says that only about 3% of mammals are monogamous, and humans fall in this category.
But then, why do they cheat?
According to the study, if your partner possesses the long allele of the dopamine gene receptor, they are probably more likely to cheat.
This video by AsapSCIENCE will probably do a better job at educating you: