The book, Mother Night, by Kurt Vonnegut, is about an American who has been raised in Germany in the interwar period, who becomes a propagandist for the Nazis, and a deep mole for the OSS.
(This is the cover of the book I first read in High School — long ago.)
The movie, starring Nick Nolte, was about as faithful to the book as you can get in cinema. Nolte is famous for portraying a burned-out human being, and this part was well done.
I recommend reading the book before seeing the movie. Either way you get the story, it is good.
Now, the thing about this is, the reason I bring it up is, it works both ways.
There are dangers to playing a role, because as human beings, our minds tend to follow what our bodies are doing. If you are looking at a picture designed to inspire lust, you will likely feel lust. If you are engaging in a vile activity, you will tend to justify it to yourself. If you will smile, you will tend to feel happy. And so forth.
This is why we have all the sit-stand-kneel during the Mass. If you are kneeling, it is very hard not to have your mind go toward humble and dependent modes. If you are standing, with your hands lifted up, it is hard not to feel praise.
Some of the Doctor Feel-Good blathers, the “Motivational Speakers” have seized on this elementary facet of human psychology and have made lots of money by abusing the principle. The whole “Whatever you can conceive and believe, you can achieve,” nonsense derives from this. But that does not take away from the reality.
Like anything else, it is a two-edged sword, ready to harm as easily as it can help. The danger is that by acting like a Howard W. Campbell, we can become a monster. The glory is that by acting like a Saint, we can become one. It is the habit of behavior which counts here. One drop of water at a time, you can fill the ocean, one step at a time, you can walk around the world. One prayer at a time, one Mass at a time, you can draw closer to God.
For myself, I am content to pretend to be a practicing Catholic, and hope for more as time goes by.