It is true. You can make yourself sick and also make yourself well by thought. When I was little, I had this childrens medical book that explained how the body fights off illness and it showed little soldiers fighting off the bad germs (remember this is a book for kids) anyway, when I am sick or in pain somewhere, I close my eyes concentrating on the area that needs to be healed and my mind heals my body. You have to believe in the power of the mind to heal though. If you keep positive thoughts ( that is really hard to do sometimes) it helps to keep the body well.