For some reason we think taking care of our body is more important than taking care of our soul. And the reason why that’s tragic is because your body is actually wasting away. Every single day your body is dying. But your soul is the same soul you are taking to eternity. You realize that?
Now if you think about this life as an ocean, and think about the boat as your heart: as long as that boat stays on top of the water- on top of the ocean (the dunya) and doesn’t let the water in, it’s fine. It stays floating and it is ok. But as soon as that boat allows water into it, that’s when it sinks.
Khushu is the soul of the prayer; that meditative state one goes into when s/he enters the prayer. The person becomes calm and enjoys the proximate relationship with Allah by moving slowly and pondering on every verse one recites.