Think of exercise as an essential nutrient for your brain, mind and body.
Wolf's Law: If you don't use it, you'll lose it. You can relate this to almost anything in the human body; muscle bulk, bone mass, learned skills in work and sports. Our body are constantly adapting to the stresses we place upon them daily. When we consistently exercise the cardiovascular system and train our weight-resistance our muscles and bone get stronger, and our mental health improves too.