Sri Aurobindo
Letters of Sri Aurobindo
Volume III - Part 4
The experience you had was simply the descent of the Divine Force into the body. By your attitude and aspiration you called for it to work in you, so it came. Such a descent brings naturally a deep inward condition and a silence of the mind, and it may bring much more – peace, a sense of liberation, happiness, Ananda. It is very often attended as in this experience by a light or luminosity. It was felt enveloping the upper part of the body down to the cardiac centre, because it is these centres, the head and heart centres that are first invaded and occupied by 
whatever descends from above, Consciousness, Force, Light or Ananda. Usually, there is at first a pressure from above on the head, then one feels something entering the higher part of the head and then the whole head is occupied, as you feel now with the fourmillement at the time of concentration. Once the head with its mental centres is open and occupied, the Force descends rapidly to the heart centre, unless there is some obstacle or a resistance in the higher vital parts. From there it sends its stream into the whole body and begins to occupy the vital and physical centres – from the navel to the Muladhara. The coming of this experience, occupation of the body by the Force from above, is a great step forward in the sadhana.
The fear of a syncope was due only to the sanskara in the mind; it must be dismissed. The Force can very well come down in the full waking consciousness; if it brings a kind of samadhi, it is usually a conscious inner condition – the consciousness taken away from outward things, but in full power within. Even if a trance came, it would be a trance and not a swoon.