Every minute of every day, your body is physically reacting, literally changing, in response to the thoughts that run through your mind. It’s been proven over and over again that just thinking about something causes your brain to release neurotransmitters, chemical messengers that allow it to communicate with parts of itself and your nervous system. Neurotransmitters control virtually all of your body’s functions, from hormones to digestion to feeling happy, sad, or stressed. Read more here.