If You Blow Air On Your Thumb, Something Incredible Happens To Your Body
This isn't some real deep, hard to understand science. Another example of this kind of thing is splashing water on your face for stress relief. It's called the "mammalian diving reflex." The splash of water causes you to hold your breath and puts a stop to the cycle of shallow breathing that accompanies stress and panic attacks.
Additionally, if you have butterflies in your stomach before a big performance or event, blow on your thumb. This regulates the vagus nerve which helps slow down the heartrate. This signals to your brain that everything is okay and you can calm down. It works every time.
What other tricks are there?