Sri Aurobindo
Letters of Sri Aurobindo
04. The Foundation of Sadhana
To quiet the mind in such a way that no thoughts will come is not easy and usually takes time. The most necessary thing is to feel a quietude in the mind so that if thoughts come they do not disturb or hold the mind or make it follow them, but simply cross and pass away. The mind first becomes the witness of the passage of thought and not the thinker, afterwards it is able not to watch the thoughts but lets them pass unnoticed and concentrates in itself or on the object it chooses without trouble.
There are two main things to be secured as the foundations of sadhana – the opening of the psychic being and the realisation of the Self above. For the opening of the psychic being, concentration on the Mother and self-offering to her are the direct way. The growth of Bhakti which you feel is the first sign of the psychic development. A sense of the Mother’s presence or force or the remembrance of her supporting and strengthening you is the next sign. Eventually, the soul within begins to be active in 
aspiration and psychic perception guiding the mind to the right thoughts, the vital to the right movements and feelings, showing and rejecting all that has to be put away and turning the whole being in all its movements to the Divine alone. For the self-realisation, peace and silence of the mind are the first condition. Afterwards one begins to feel release, freedom, wideness, to live in a consciousness silent, tranquil, untouched by any or all things, existing everywhere and in all, one with or united with the Divine. Other experiences come on the way, or may come, such as the opening of the inner vision, the sense of the Force working within and various movements and phenomena of the working etc. One may also be conscious of ascents of the consciousness and descents of Force, Peace, Bliss or Light from above.