Use it or lose it

Use it or lose it is the colloquial definition of neuroplasticity, defined in more technical terms by BetterHelp online in its, February 19, 2025, article "What 'Use It Or Lose It' Means in Neuropsychology":

Neuroplasticity is the ability of the central nervous system to form and reorganize neural connections in response to injury or a learning event. This trait allows the human brain to adapt and change depending on events or experiences. Human brains can adapt through learning when an individual practices a task repeatedly. However, if they do not follow through with this repetition, this adaptive ability is lost, and they lose these possible new neural pathways until they return to the practice. This phenomenon is often referred to as the central nervous system's "use it or lose it" insurance policy.