Mens sana in corpore sano - Latin proverb, full of truth.
If our body is sick our minds will suffer - mental deficiency, poor memory capacity, inability develop certain themes ...
If our mind is not healthy, nor body will not be. Most actions that take place inside our bodies are dictated by the brain. Even cellular reproduction. If some mechanisms in the brain are damaged, the whole body will suffer.
So, mind and body are closely related. Both should work properly.