I was quite in earnest in speaking of the progress you had made by the psychic movement and the endeavour to detect and remove the ego. I had already written to you strongly approving of that way. It is in our Yoga the way to devotion and surrender—for it is the psychic movement that brings the constant and pure devotion and the removal of ego that makes it possible to surrender. The two things indeed go together.
The other way, which is the way to knowledge, is the meditation in the head by which there comes the opening above, the quietude or silence of the mind and the descent of peace etc. of the higher consciousness generally till it envelops the being and fills the body and begins to take up all the movements. But this involves a passage through silence, a certain emptiness of the ordinary activities—they being pushed out and done as a purely superficial action—and you strongly dislike silence and emptiness.
The third way which is one of the two ways towards Yoga by works is the separation of the Purusha from the Prakriti, the inner silent being from the outer active one, so that one has two consciousnesses or a double consciousness, one behind watching and observing and finally controlling and changing the other which is active in front. But this also means living in an inner peace and silence and dealing with the activities as if they were a thing of the surface. (The other way of beginning the Yoga of works is by doing them for the Divine, for the Mother, and not for oneself, consecrating and dedicating them till one concretely feels the Divine Force taking up the activities and doing them for one.)
[Sri Aurobindo: Letters on Yoga]