Neuroplasticity.
Neurons that fire together, wire together.
Every thought you repeat, every emotion you feel, physically shapes your brain. Connections strengthen with use. The more often a circuit fires, the more efficient and the more automatic it becomes. This is no longer a metaphor. It is measurable in tissue.
Watching a movie of your vision exercises the neurological hardware that runs that vision. It stops being a distant place you have to push toward and starts being the path of least resistance.