We all want to improve our health, our wellness and our happiness.
But despite our good intensions, we often fail to act on them and even if we do, it’s ephemeral.
There’s no doubt about it: change is hard. And no matter how hard we try to change, the comforts of eating sugary snacks, shopping and online surfing and difficult to resist.
We try everything, but despite our unremitting effort to change, we return to our vices and greater voracity.
Why do we fail to break bad habits?
To answer that question, we need to look at our ability to judge our impulsive behaviours, or rather, our perceived ability.
How The Illusion of Self-Control Promotes Bad Behaviour
In 1999, researchers at Northwestern University asked a group of smokers to take a self-control test. 
Unknown to the participants, it was simply a word association test. The researchers randomly labeled half the group as having high self-control and half as having low self-control.
After hearing their supposed results, participants played a game that involved watching the 2003 movie Coffee and Cigarettes while refraining from having a cigarette and challenging themselves with one of four levels of temptation. Each had its own cash reward.
They could keep a cigarette unlit in their mouths (for the most money), unlit in their hand, on a nearby desk or (for the lowest reward) in another room.
Participants earned a prize only if they avoided smoking for the entire 95-minute film.
Here’s where it gets interesting. Smokers told that they had high self-control exposed themselves to significantly more temptation than their counterparts – opting on average to watch the movie while holding a cigarette – and they failed to resist lighting up three times as often as those told they had low self-control.
The smokers who failed to refrain from smoking fell victim to “restraint bias”: the tendency to overestimate one’s ability to control one’s impulsive behaviours.
Restraint bias is common; we think, “I can resist temptation”, but we an inflated self-control belief, we greater exposure ourselves to temptation and increase our impulsiveness.
“Restraint bias offers insight into how our erroneous beliefs about self-restraint promote impulsive behavior”, writes professor Loran F. Nordgren of Northwestern’s Kellogg School of Management. “It helps us to understand puzzles in addiction research such as why recovered addicts often relapse after they have broken free of withdrawal symptoms”.
If we predetermine what our future obstacles are, we can avoid goal-threatening distractions or, at the very least, reduce their interruptions.
In order to initiate and maintain good habits, therefore, we need a strategy. That strategy is using “implementation intentions”.
How to Break Bad Habits
In 1999, in a paper entitled “Implementation Intentions: Strong Effects of Simple Plans”, psychologist Peter Gollwitzer introduced a self-regulatory strategy to help habit and behaviour modification:
Implementation intensions are if-then plans that spell out in advance how one wants to strive for a set goal. For the if-component, a critical cue is selected (e.g., a good opportunity, an anticipated obstacle) that is linked to a goal-directed response in the then-component. 
Implementation intensions are effective because, with repetition, they become habits themselves; no longer do you need to motivate or will yourself to overcome obstacles. You have an exit strategy.
Goals are often abstract, “I’m going to exercise”, but implementation intensions are specific, “On Monday, Wednesday and Friday, after breakfast, I will pick up my gym bag, drive to the gym and exercise for 30 minutes”.
If and when obstacles do arises, you’ll be prepared for them. You’ll have more awareness and won’t deliberate on what to do; decision fatigue won’t corrupt you and your preventive procedure will feel natural.
How You Can Use This
You can use implementation intensions to plan when and where we’re going to do our goal-directed habit, and what you’re going to do in the event of an obstacle.
For example, if we return to the aforementioned example:
On Monday [DAY], after I’ve finished eating my breakfast, I will pick up my gym bag [CUE], drive to the gym [PLACE] and exercise [ROUTINE] for 30 minutes [TIME].
You might also plan you’re ‘if-then’ strategy:
Example 1: If I have the urge to watch Internet pornography, then I’ll go for a 30-minute walk.
Example 2: If a coworker offers me a sugary snack, then I’ll politely decline and explain I’m on a diet.
Example 3: If I want a cigarette, then I’ll call a friend.
The lesson here is simple: when you’ve made progress avoiding your indulgences and you hear your self-talk telling you it’s okay to expose yourself to temptation again – ignore it.
The first mistake is an accident. The second is a choice. The third is a habit.
 Nordgren, L. F., Harreveld, F. V. and Pligt, J.V.D. (2009) ‘The Restraint Bias: How the Illusion of Self-Restraint Promotes Impulsive Behavior’, Psychological Science, 20(12), pp. 1523-1528.
 Gollwitzer, P.M. (1999) ‘Implementation Intentions: Strong Effects of Simple Plans’, American Psychologist, 54, pp. 493–503.