Mantra should be received from a guru. A book cannot determine the correct mantra for you. Just as a cartridge needs to be struck by the hammer of the gun in order to fire, so the mantra needs to be struck by the hammer of the guru in order to explode the consciousness. The relationship between the guru and disciple is only the mantra. When guru gives mantra to the aspirant, he becomes a disciple. One who is working with and developing the mantra is a disciple. With the help of the mantra, he is trying to fix the samskaras, the different formations of the mind.
The guru has to decide the mantra for you on the basis of your zodiac sign, temperament, illness, or spiritual path. After receiving the mantra from your guru, you must practise it every day for five to ten minutes. No matter how powerful your mantra is, unless you practise it, you will gain nothing.
The mantra has to be repeated thousands of times. In the beginning you repeat it on the audible plane. The vibrations are external and the effects are gross. But gradually, as your mind becomes quieter and quieter, the vibrations grow more powerful. The mantra then goes deeper into the consciousness, pierces through the conscious mind and the subconscious mind and penetrates into the unconscious mind. Once the mantra enters into the unconscious mind, it destroys all samskaras and mental formations. Therefore, the mantra must be repeated regularly with the mala. If your mantra is Om, practise five malas every day. If you don’t have time in the morning, do it at night. Many householders never practise mantra at night because they are confused about certain taboos. They feel that it is not proper to practise mantra after maithuna, but according to tantra, the effect of mantra is far greater at this time. So if you have fixed five malas each night, you must do it. Regardless of what sort of life you lead, practise first and then sleep.
The mantra is a purifying force. Nothing in the world can pollute the mantra; nothing can make it impure. Mantra can purify all corruption. It is such a great purifier that no matter what you eat, how you live, what you think, or which religion you belong to, it will dominate and destroy all the samskaras. When the samskaras are destroyed and the veil is split asunder, you will see the divinity shining like the sun before you. What you have been searching for is not far away. There is only a veil between you and me, which has to be destroyed by the mantra shakti, mantra yoga. Om is the most powerful, the most benign of all the mantras.
Swami Satyananda Saraswati