Have you ever heard of Psychneuroimmunology?
It's one 'mouthfull' of a word isn't?
In very simple terms, it is the science of the mental outlook on the immune system. You may have been called a "pain in the neck" as a child, or heard"I'm so scared, I'm sick to my stomach."
There are more examples, but I am sure that you get the point. There is a lower recovery average after surgery for those with a negative attitude. Many wounds that are not severe become infected when a person has a attitude of imminent death.
And many grievous wounds are healed in those who are too stubborn to die. Remember a healthy attitude can do a lot to help prevent illness. You have probably heard of several people telling a healthy person that they look sick and eventually, they are sick and go home.
Keep telling yourself that you are healthy and happy, and you stand a better chance of good health. If you do fall ill, keep telling yourself that this is only temporary and that you are feeling better already and you will recover faster.
Here is a link where you can read a bit more on the brain body connection http://en.wikipedia.org/wiki/Psychoneuroimmunology.