The intention to suppress a response has the paradoxical effect of strengthening it.  In the "Tell‑Tale Heart," Edgar Allan Poe described the Imp of the Perverse. An example: 

Try not to scratch your nose. Continue reading, but be aware that even letting your nose itch would indicate a lack of personal control. So try not to even think about your nose, and see if you can read to the end of this article without once scratching your nose or the area around it.  

The intention to not let your nose itch ‑ especially if you take it seriously ‑ may have the perverse consequence of causing the very behavior you are trying to prevent.  This is true even if the behavior initially had a low probability.  Some causes of counter-intentional behavior are described below: 

Negative Suggestion

Negative representations are defined in terms of positive representations [their opposite], but positive representations are defined directly.  For example, the statement: "It is not raining" requires a representation of:  "It is raining."  The statement: "Chester is not a pedophile." requires the audience to comprehend the assertion: "Chester is a pedophile," and then reject it.  But the association between Chester and child molestation now has a representation in the audience's mind.  Likewise, to understand the instruction: “Don’t let your nose itch!” the reader must refer to an internal representation of an itchy nose - which causes the nose to itch.  

Ironic Processes

Another semantic source of counter‑regulatory motivation: To determine if you are successful in having a nose that is not itching, you must compare the current sensations with what they would be if your nose was itching.  In this case, it is checking to make sure you are successful that causes the nose to itch.  Ironic, isn't it? 

To avoid semantic sources of counter-regulatory motivation:  Always frame intentions in terms of what you want, not what you don't want.   

Reactance

Humans hate restrictions ‑ especially of those freedoms they already have.  Reactance refers to the motivation to react or rebel against restriction.   For example, in one study, two-year old boys accompanied their mothers into a room containing equally attractive toys. The toys were arranged so that one stood in front of a transparent Plexiglas barrier, and the other stood out of reach behind the barrier. The boys showed a strong preference for the toy they couldn't have. Their inability to get the toy behind the barrier caused many boys to tantrum,  which was not relieved by giving the child the equally attractive toy. 

Once an object [such as chocolate, alcohol, etc.] is forbidden there is an emotional reaction to the restriction, which, perversely, enhances the desire for the forbidden object.   

                  Restrained Eaters Research

Because the motivation for a fit body or a sober life resides within the person, it rises and falls with one’s emotional state.  When the person is highly motivated - usually in the beginning - there is no problem.  However, as discussed above, counter‑regulatory motivation is intrinsic to the task, and so is not dependent on passing emotional states.  So whenever internal motivation wanes, even for a moment, there is risk of a first lapse. 

Understanding counter-regulatory motivation is the key to good long-term outcome.  However, studying it is difficult; we hide our perverse nature when we think we are being observed.  Consequently, a deceptive methodology has been developed to study it.  Dieters [restrained eaters] and non‑dieters are told that they are participating in a taste preference study. After sampling a variety of foods [the pre‑load] and offering their critique, they are "thanked" for their participation with a free lunch. The lunch is offered buffet style, and each participant can consume as much as desired. Unbeknownst to the participants, behind one‑way mirrors are research staff observing them and calculating how many calories each subject consumes. The effect of low calorie and high calorie pre‑loads on subsequent eating are compared.  

When the pre‑load was low calorie, dieters consumed fewer calories during the buffet than did non‑dieters ‑ after all, they were on a diet. However, when the pre‑load was high calorie, dieters consumed significantly more calories during the buffet than those who were not dieting!  

Interpretation of these results: After consuming the high calorie pre‑load, the restriction was temporarily removed, for example: "I have already broken my diet ‑ I'll start back tomorrow."  The idea that there will be a restriction in the future paradoxically enhances the motivation to act counter to the restriction - "to get it while I can."   The urgency to take advantage of the apparently limited opportunity produce extreme and bizarre behavior once a lapse as occurred.  Other processes that can turn a first lapse into a destructive relapse are described in Illusions of the Psyche [PIG # 6].  

             The Insult that adds to the Injury

\Dieters interpret their repeated failures as proof of personal weakness.  This is an internal attribution for failure - the cause of the problem is within the person.  They may also conclude that the causes of failure are stable - for example: “The same weaknesses that caused me to fail in the past, will cause me to fail in the future.” 

An alternative understanding: the very intention to restrict eating produces counter-regulatory motivation.  The occurrence of a single lapse may trigger other lawful processes which lead to relapse.  Here past dietary failures are attributed to causes external to the person - universal motivational processes.  If the person develops an appreciation of the true nature of the task and changes strategies, the outcome will be different.  

Consider the following study of how counter‑regulatory motivation can influence self‑perception. Teen‑aged boys were told that a book was too sexually explicit to be read by those under 21. This restriction had the effect of dramatically increasing their desire to read the book.  The experimenters knew that the attractiveness of the book was enhanced because the book was forbidden. But the boys had a different perspective; they attributed their motivation to read the book to a personal characteristic to be attracted to such content. Forbidding the book had the perverse consequence of causing the subjects to believe that they were perverse.

Attributing dietary failures to personal inadequacy is not only naive, it is counter-productive.  If you want to be among the small proportion who achieve good long‑term outcome, you cannot afford the luxury of this mis‑attribution.  The failure of weight loss programs and diets are due to the operation of lawful psychological principals.  They can be described in writing because, in one form or another, they apply to everyone.  Yet each of us have been dealt a unique genetic hand, and we each have a history full of unusual events.  The interaction between the general principals and the particular human is the domain of personal work with your therapist.