When I was in the 4th grade I was obsessed with mood rings and glitter. I realized after my fourth mood ring that the colors could be changed by putting the ring under water.
Cold water would turn the ring dark blue, dark red and if the water was really cold the ring would turn completely black. When the ring was put under warm water the opposite would happen. The ring would turn a light green or violet. It didn’t take a rocket scientist or someone older than 10 to realize that mood rings worked according to body temperature. Meaning that when the ring is green and you’re happy your body is also warm. On the other hand when the ring is of an amber hue and you are feeling tense your body is also cold. Much like when you get goose bumps from feeling frightened or chilly. Once I put two and two together I knew that our body temperature changes due to our emotions.
To make a long story short your mind is so powerful that it can change your body temperature thus the way your body reacts to the environment. Your body is the minds form of communication. This is why you often see perfectly healthy people who happen to always be sick. What they are is sick is in the mind. And that, my friends is what I learned from observation when I was nine thanks to my obsession with mood rings.