I found this, really good:
What is Disloyal Fog?
~Author, anonymously known as “Pit-of-my-stomach” on Talk About Marriage forum
Adapted, with permission, from the thread “Never Say Never”
I don’t think the majority of people involved in affairs, or even drugs for that matter, set out with the intention of becoming drug addicts or adulterers. It is a snow ball effect. Most people don’t even know it’s rolling until its already gained significant speed and can very easily get out of control.
The Disloyal Spouse doesn’t always realize what is happening or they see it through “the fog.” A bad (often dismissed as “innocent”) decision starts the ball rolling, which forces another bad decision, which may be difficult to cope with, which is rationalized, which kicks in all of the defense mechanisms, which force more bad decisions…. Etc, etc, etc…
You are not as strong as your mind, and in affair situations your mind IS ON DRUGS. It most often starts as something “innocent”… Chemicals get naturally released into the brain–fed small doses of “love drugs” i.e. phenyl ethylamine (or “PEA” — a naturally occurring trace ammine in the brain. PEA is a natural amphetamine, which releases Dopamine. Dopamine stimulates the production of oxytocin). This begins “intrusive thinking,” where it seems like your brain is fixated on the object of your affection. When your heart rules your head, there’s actually one part of your brain running the other: the cortex is the area of your brain that controls logical thinking, while emotions are processed by the limbic system. When too many happy chemicals like PEA and dopamine flood your brain, they head straight for the limbic system.
The Disloyal Spouse is now on the addiction path. Then their mind can begin a process of defensive mechanisms which can and will shield them from realizing what is really happening, and before they know it–they lose control. But most often I believe the Disloyal Spouse thinks they are in control of the situation as does any “addict”. They don’t see it; after all that IS a defense mechanism. It’s your mind’s way of protecting itself, an unconscious process that tries to reduce the anxiety associated with instinctive desires. The most well known and common defense mechanisms in the mind of an adulterer would be Denial, Rationalization, and Repression.
Denial is probably one of the best known defense mechanisms, used often to describe situations in which people seem unable to face reality or admit an obvious truth (i.e. “more than friends”) Denial is an outright refusal to admit or recognize that something has occurred or is currently occurring.
Denial functions to protect the ego from things with which the individual does not want to cope (for example, guilt). While this may save us from anxiety or pain, denial also requires a substantial investment of energy. Because of this, other defenses are also used to keep these unacceptable feelings from consciousness.
An example of denial might be: “I know we texted and talked on the cell phone for 6000 minutes this month, but we’re just friends! It’s not an emotional affair!
Rationalization is a defense mechanism that involves trying to explain an unacceptable behavior or feeling in a rational or logical manner, avoiding the true reasons for the behavior. Rationalization not only prevents anxiety, it may at the time seem to protect self-esteem, self-concept, and personal dignity. Rationalization can kick in when confronted by perceived moral failure or wrongdoing (for example, on Discovery Day); people tend to blame other people or outside forces rather than take personal responsibility.
An example of rationalization might be: “You ignored me when I wanted to talk so I have a right to find someone who pays attention to me” or “I never did love you–I’ve been unhappy for YEARS so I found someone else.”
Suppression is another well-known defense mechanism. Suppression acts to keep information out of forefront of your conscious awareness (for example, selective memory regarding conversations or acts with the Other Person). Sometimes we do this consciously by forcing the unwanted information out of our awareness, which is known as repression
An example of suppression might be the Disloyal Spouse claiming to “forget” when they first had sex with the Other Person–claiming “I don’t know.” An example of repression might be the Disloyal Spouse purposefully “forgetting” how happy they were just last Christmas.
Sublimation, Displacement, Projection and Intellectualization are other defense mechanisms which play small parts in the process of mental self protection in affair or addiction situations…
Often the Disloyal Spouse attributes “outside forces” to what happened that lead to an affair (for example. “it just happened”). Outside forces don’t get people into these situations, but “inside forces” can… Thus, a person is responsible for their actions and the decisions they made to get to that point. Your brain + the love drugs (amphetamine, oxytocin, dopamine, etc. …) + addiction defense mechanisms can lead to situations that put your marriage and family in jeopardy. So protect yourself and your marriage! It could happen to almost anyone, don’t kid yourself!