The Journal of Consumer Research published a study examining the use of linguistics and self-talk in decision making. They brought in 120 undergraduates who were trying to eat more healthily.
When faced with temptation, one group was told to say, “I can’t” and another group, “I don’t”. On the surface, both words have a similar effect – two slightly different ways of saying “no”. However, the difference is internal.
“When it is obvious that the goals cannot be reached, don’t adjust the goals, adjust the action steps.” – Confucius
When you say, “I don’t”, you are making a choice not to do something and choices are physiologically empowering. You confirm to yourself that do have the strength and willpower to say no. On the other hand, “I can’t” is a restriction, something you want to do is being blocked. It undermines your sense of free will.