He must think as often and as intently of the Overself as an infatuated girl thinks of the next appointed meeting with her lover. His whole heart must be held captive, as it were, by this aspiration. This is to be practised not only at set formal times but also constantly throughout the day as an exercise in recollection. This yoga, done at all times and in all places, becomes a permanent life and not merely a transient exercise. This practice of constant remembrance of the Overself purifies the mind and gradually renders it naturally introverted, concentrates and eventually illumines it.
-- Notebooks Category 23: Advanced Contemplation > Chapter 6: Advanced Meditation > # 217