It's amazing how clearly my physical condition affects my outlook, mood, feelings, and even thoughts. It's extremely obvious that we live in a physical world. We have physical bodies, we use physical things, and we need physical objects to live our lives. There is more though: beyond my corpse, I have a soul, which cannot be touched, seen, or felt. I am part of another world that has no physicality. For now, both of these exist at the same time and in the same place (inside of me), but it's not always obvious that they have a relationship with one another.
When my body feels good, my thoughts are processed through a healthy object "in good standing." But when I am not in good shape physically (due to injury, sloth, sickness, or just aches and pains), my soul knows it. Maybe my point of view gets selfish or critical, my remarks turn sarcastic and harmful, or maybe my mood becomes negative and depressed. Anyway you look at it, it's important to know that these to "worlds" are connected.