Emptiness

Emptiness is not in itself a bad condition, only if it is a sad and restless emptiness of the dissatisfied vital. In sadhana emptiness is very usually a necessary transition from one state to another. When mind and vital fall quiet and their restless movements, thoughts and desires cease, then one feels empty. This is at first often a neutral emptiness with nothing in it, nothing in it either good or bad, happy or unhappy, no impulse or movement. This neutral state is often or even usually followed by the opening to inner experience. There is also an emptiness made of peace and silence, when the peace and silence come out from the psychic within or descend from the higher consciousness above. This is not neutral, for in it there is the sense of peace, often also of wideness and freedom. There is also a happy emptiness with the sense of something close or drawing near which is not yet there, e.g. the closeness of the Mother or some other preparing experience. What you describe is the neutral quiet. There is no need for anxiety. When it comes, one has only to remain quiet and open and turned to the Mother till something develops from within.

Ref : Letters on Yoga Vol. III