If you actually did it it would not be a simple affirmation for long, your mind will quickly start to wander as the act of writing the same thing over and over becomes more automatic and what your mind will wander towards is what you are writing and staring at. The brainwashing that is happening is that of brainwashing you to set aside a part of your day for sustained focused thought on your goals, something most people seem to have never learned, they learned to ask their guidance concealer and google and internet forums but never themselves.