how often to practice self-enquiry

D.: Is it enough if I spend some time in the mornings and some time in the evenings for this atma-vichara? Or should I do it always - say, even when I am writing or walking?

M.: Now what is your real nature? Is it writing, walking, or being? The one unalterable reality is Being. Until you realise that state of pure being you should pursue the enquiry. If once you are established in it there will be no further worry. No one will enquire into the source of thoughts unless thoughts arise. So long as you think "I am walking," "I am writing," enquire who does it. These actions will however go on when one is firmly established in the Self. Does a man always say, "I am a man, I am a man, I am a man," every moment of his life? He does not say so and yet all his actions are going on.

~ Talks with Sri Ramana Maharshi