On the Gayatri Mantra
Sri Aurobindo: Do you know the meaning of the Gayatri Mantra?
Vyas: It is a great Shakti — power — but I do not know the meaning.
Sri Aurobindo: It means: “We choose the Supreme Light of the divine Sun; we aspire that it may impel our minds.”
The Sun is the symbol of the divine Light that is coming down and Gayatri gives expression to the aspiration asking that divine Light to come down and give impulsion to all the activities of the mind.
In this Yoga, also, we want to bring down that divine Sun to govern not only the mind but the vital and the physical being also. It is very difficult effort. All cannot bear the Light of the Sun when it comes down. Gayatri chooses the Divine Light of the Truth asking it to come down and govern the mind. It is the capacity to bear the Light that constitutes the fitness for this Yoga.
You can meditate on this Mantra, keeping in mind the meaning, and you can aspire also to become fit for this Yoga. When you are able to fix your mind you may remember any one of the forms of the Godhead. You can pray to your Ishta-Devata that he may make you fit 
for this Yoga and that it may come and work in you.
Really speaking, this Yoga is not done by the power of man: it is done by the Divine Power and so She can bring about every change in the capacity of the Sadhaka.
You should direct the aspiration towards the Supreme. When you have succeeded in doing it, you should watch all your inner activities and see what they are. Whatever you find there you must calm down. This calm you must go on deepening, so much so that you should feel quiet, wide, large in consciousness. If you can establish this calm you will be able to do this Yoga.
The calm must become deep and so settled that even while doing ordinary work you should feel it within yourself and see the activity as something quite separate from yourself.
You should have a fixed time for meditation and must be regular in doing it. You can write about your experience from time to time.
