grown-up can do. Most adults have little patience and capacity for such an undertaking, and as such, are strongly motivated to accept things the way they are and even make up reasons for actively working to keep things the same.
Take for instance changing an all-pervasive habit such as a facial tic. In a situation as this, the reasons why a person would want to make this change would not be fully experienced until the change had been made.
The main problem in influencing this mannerism is it seems to repeat itself automatically without registering that anything has intentionally happened. People around someone with a facial tic would try to ignore it also and never bring up the uncontrollable characteristic of it, even though it's distracting to remember to disregard the tic as a meaningless gesture. If the person with the problem was a woman and she thought of designing a strategic feedback of the event for herself, perhaps braiding her hair so a strand hung down over her face would help her feel a new
sensation as her face rubbed against the braid. This way she could be aware right before she was beginning to start the habitual expression and thus be able to begin to interrupt herself doing it.
Also an important point of improvement would be her response to unsuccessful prevention of the action. Changing an action such as this would be discouraging at first if she didn't appreciate how many times her body/mind had practiced this activity and how difficult the challenge really is. The most likely outcome of her experiments would be that her will to do differently would be quite unsuccessful at first. She would be very lucky to have even partial success. This would be because after not very long, she would tend to disregard her strategic indicator!
Habits are extremely tricky and coersive. Their complete and utter invasiveness is justified by a very strong sense of self-preservation gone wild. They have everything to do with you - because you designed them to address some intention of yours, or you let them run wild and legislate how you are spending your energy without doing anything about how your habits affect you.
I'm saying this from my own experiences at changing the way I would breathe and speak - which was challenging in a very similar all-pervasive way. The greatest moment comes when you suddenly realize or remember the intention that was usually lost in the past when you installed the habit.
It comes as an insight as you're staying with yourself moment to moment. Sometimes it's such a complete insight that the need for the habits drops away instantly. My insight concerning the way I'd learned to talk was that somehow as a child who did not want to seem threatening, I learned to take a breath, let it out and then start talking on the most tiniest bit of air possible. In spite of the insight, it still took me some very attentive work over a two year period before I could take the first free breath of my life without unnecessary pressure and force...and then let it out while I began to talk, no big deal, over and over again like most people with beautiful voices can talk.