The disturbances are clearly visible on your physical body. Also in hot summer body starts sweating to maintain the inner temperature of the body with the outer environment. The process of sweating is involuntary and continuous as per the predetermined program set in your mind. Here the atmospheric temperature is an outside obstruction , which is resisted by the vital force within the body. The balance obtained through perspiration.
Same principle is visible in fever.
The increase in body temperature is just to resist the parasitic attack and is controlled by nervous system of the body. Thus we have seen that the body resists the obstructions all the time and survival is sought. When the vital force becomes weak makes the body susceptible to various diseases. It is not necessary that the obstruction will be of long lasting nature and affecting the psyche for a longer period, even the simplest one can bring abnormalities in your healthy way of life for a time being. Take for e.g.