We all are actors. It's not even "Fake it, 'till you make it", because everyone keeps acting, even after he "made" it.
Actors often stay in character all the time on set, often even off set, during the production of the movie. And while it might be true that certain personalities are cast for certain rolls, it's also true that the role rubs of onto the actor.
Our habits is what defines us. If we say we would act the roll of a body builder and went to the gym every day, we would develop the habit of going to the gym each day. And we would develop muscles as well. We would become a body builder, even though we only acted as if we were one. But if we stop acting, stop "faking", "pretending" to be a body builder, and wouldn't hit the gym as often any more, we would lose it again.
If you act as if you were a person that always arrives 15 minutes early, you will become this person. At least for the time that you hold this act up. And you can hold it up as long as you like.
Similarly you can act as if you would always focus on the most important things first. And as if you would always be hyperaware about your surroundings, your emotions. Meditation and mindfulness. You don't have to act this for others, but for yourself. Because if you only act this for others, it might be faking. You could go through the motions without meaning it. But if you act it for yourself, it's like role playing.
In the movie Man on the Moon, Jim Carrey "is so committed to the role that, like Andy, he had difficulty separating himself from the character. Carrey's performance becomes so real that people who had known Andy, even family and others close to him, felt like they had him with them again.", according to the documentary about the production of this movie.
Emma Watson was cast as Hermione Granger when she was eleven. She might have been smart back then, but exceptional? With sixteen (in June 2006), "she took GCSE school examinations in ten subjects, achieving eight A* and two A grades". Later, she started a PhD at Oxford University.
He locked himself up