With practice, duality disappears and Samadhi, or the superconscious state, is reached. Do not become impatient, as this takes long time. In Samadhi one rests in the state of bliss in which the Knower, the Knowledge, and the Known become one. This is the superconcious state reached by mystics of all faiths and persuasions. If you meditate for half an hour daily, you will be able to face life with peace and spiritual strength.
Meditation is the most powerful mental and nerve tonic.
Divine energy freely flows to the adept during meditation, and exerts a benign influence on the mind, nerves, sense organs and body. It opens the door to intuitive knowledge and realms of eternal bliss. The mind becomes calm and steady. Meditation and Mantras by Swami Vishnu-devananda . You can also find more information on the page describing the 8 limbs of Raja Yoga.