Every time you tell yourself “I can't”, you're creating a feedback loop that is a reminder of your limitations. This terminology indicates that you're forcing yourself to do something you don't want to do.
In comparison, when you tell yourself “I don't”, you're creating a feedback loop that reminds you of your control and power over the situation. It's a phrase that can propel you towards breaking your bad habits and following your good ones.
“I can't” and “I don't” are words that seem similar and we often interchange them for one another, but psychologically they can provide very different feedback and, ultimately, result in very different actions. They aren't just words and phrases. They are affirmations of what you believe, reasons for why you do what you do, and reminders of where you want to go.
The ability to overcome temptation and effectively say no is critical not only to your physical health, but also to maintaining a sense of well–being and control in your mental health.
To put it simply: you can either be the victim of your words or the architect of them. Which one would you prefer?