The heat in the body is due simply to the working that is going on within; it is what is called the heat of tapas,there is nothing unhealthy in it as in the heat of fever.
The heat is the result of the psychic fire burning away obstacles, the coolness and complete quietude come as a result. It is true that if the consciousness remains quiet, the psychic will manifest more and more from deep inside and a clear feeling will come of what is true and spiritually right and what is wrong or untrue and with it also will come the power to throw away what is hostile, wrong or untrue.
The feeling of warmth in the heart comes sometimes from the approach of Agni fire, sometimes from that of love or Ananda, sometimes simply from a touch of the Force.
How the body receives the higher dynamism depends on the condition of the body or rather of the physical and most material consciosness. In one condition it is tamasic, inert, unopen and cannot bear or cannot receive or cannot contain the force; in another, rajas predominates and tries to seize on the dynamism, but wastes and spills and loses it; in another, there is receptivity, harmony, balance and the result is a harmonious action without strain or effort.