Sri Aurobindo
Letters of Sri Aurobindo
10. Experiences and Realisations
The reason why there are these alternations of which you complain is that the nature of the consciousness is like that; after a little spell of wakefulness it feels the need of a little sleep. Very often in the beginning the wakings are brief, the sleeps long; afterwards it becomes more equal and later on the sleep periods are shorter and shorter. Another cause of these alternations, when one is receiving, is the nature’s need of closing up to assimilate. It can take perhaps a great deal, but while the experience is going on it cannot absorb properly what it brings, so it closes down for assimilation. A third cause comes in the period of transformation,– one part of the nature changes and one feels for a time as if there had been a complete and permanent change. But one is disappointed to find it cease and a period of barrenness 
or lowered consciousness follow. This is because another part of the consciousness comes up for change and a period of preparation and veiled working follows which seems to be one of unenlightenment or worse. These things alarm, disappoint or perplex the eagerness and impatience of the sadhak; but if one takes them quietly and knows how to use them or adopt the right attitude, one can make these unenlightened periods also a part of the conscious sadhana. So the Vedic Rishis speak of the alternation of “Day and Night both suckling the divine Child.” What you feel in the head is probably the first conscious descent into the body of the divine Force from above. Up to now it must have been working unfelt by you from behind the heart. If the concentration takes place naturally in the head you must allow it to do so, but the possibility of this has been prepared by the previous concentration in the heart, so that also need not be discontinued unless the force working in you insists on the upper concentration only. Aspiration can be continued in the same way until the conduct of the sadhana by the Mother’s power is clearly felt and becomes to you the normal thing.