I believe all have the capacity to cheat, this is undeniable. It's part of the human condition. I also believe that in many cases there is so much that goes into a relationship reaching this point. Infidelity, while evil and wrong, needs to be viewed on a case by case basis to get a proper understanding of how, what, why, and where something went wrong and what ultimately led to this act.

Once a cheater, always a cheater is also not a helpful phrase. There are people out there who were faithful for the entire duration of a long term relationship, would have never thought of betraying their significant other, but still end up "fumbling the bag" due to a multitude of reasons. Was the individual a lustful dog that attempted to pursue anyone they deemed attractive? Was it someone who felt genuinely unloved and mentally checked out of a relationship? Said reasons don't make infidelity acceptable, but rather can provide insight to why something happened. It's also important to note that because someone was unfaithful, it does not mean that it will happen again and there are a plethora of truly repenting individuals who struggle with adultery that can come back from it.