You must not fear. Most of your troubles come from fear. In fact, ninety per cent of illnesses are the result of the subconscient fear of the body. In the ordinary consciousness of the body there is a more or less hidden anxiety about the consequences of the slightest physical disturbance. It can be translated by these words of doubt about the future: “And what will happen?” It is this anxiety that must be checked. Indeed this anxiety is a lack of confidence in the Divine’s Grace, the unmistakable sign that the consecration is not complete and perfect.
As a practical means of overcoming this subconscient fear each time that something of it comes to the surface, the more enlightened part of the being must impress on the body the necessity of an entire trust in the Divine’s Grace, the certitude that this Grace is always working for the best in our self as well as in all, and the determination to submit entirely and unreservedly to the Divine’s Will.
The body must know and be convinced that its essence is divine and that if no obstacle is put in the way of the Divine’s working, nothing can harm us. This process must be steadily repeated until all recurrence of fear is stopped. And then even if the illness succeeds in making its appearance, its strength and duration will be considerably diminished until it is definitively conquered.
Ref : Words of The Mother Vol. II