Even the pranas, the vital forces, will not cooperate properly, because they were secure earlier by depending on external factors. Now you want that you should be secure intrinsically by not depending on any external media. Everyone resists change. If you introduce some change in the programme of life, it is resisted immediately. Everybody is against any kind of reformation, change, or instruction for something different from what is taking place now.
Soldiers can fall sick a day before war takes place.
Malingering is one of the features that we may have to face. The pranas are associated with the physical body in one way. When you concentrate the mind in meditation, the pressure you exert on the mind tells upon the prana also. This pressure which the prana feels is communicated to the entire physiological system. Any kind of pressure is an interference of some sort.