Many people say, “Oh, yes, here I am not afraid.” They don’t have any fear in the mind, their mind is not afraid, it is strong, it is not afraid; but the body trembles, and one doesn’t know it, because it is in the cells of the body that the trembling goes on. It trembles with a terrible anxiety and this is what attracts the illness. It is there that you must put the force and the quietude of a perfect peace and an absolute trust in the Grace. And then, sometimes you are obliged to drive away with a similar force in your thought all suggestions that after all, the physical world is full of illnesses, and these are contagious, and because one was in contact with somebody who is ill, one is sure to catch it, and then, that the inner methods are not powerful enough to act on the physical, and all kinds of stupidities of which the air is full. These are collective suggestions which are passed on from one person to another by everybody.
Ref: Questions and Answers 1955