A broken arm carried in a sling for a period of time will shrink in size and in most cases lose most of its strength and even after it is free will always take days to return to former state.
This is the same case with a person who follows a routine or particular way of doing things everyday with no urge for improvement and not trying out new ways or pattern of solving problems.
A mind which is not keep active through repeated learning will likely lose much of its brilliance and as such its logical to always exercise your mind and intellect as much as you seek to exercise your physical body inorder to keep it in shape.Learn new ways of doing things, add new skills, solve a problem differently and you will get better
