«If you don’t use it, you lose it» means that skills, knowledge, and physical abilities decline or disappear without regular practice, applying to muscles that atrophy, brains that lose neural connections, and talents that fade, emphasizing the need for continuous engagement to maintain function.

Decline or disappear without regular practice!

This principle of neuroplasticity and physical maintenance shows that consistent effort is required to retain abilities, from playing an instrument to staying fit.