Manan means 'involvement with thought. This involvement with thought in the negative form becomes worry, chinta. As a positive thought or in the positive dimension it becomes manan, reflection. How do you know the difference between reflection and worry? In reflection, your mind stays peaceful, whereas in worry your mind becomes agitated. The process is the same as you are becoming involved and absorbed in your own thoughts. However, when you can maintain your objectivity those thoughts are known as reflection. When you cannot maintain your objectivity and you become involved those thoughts are known as worry.
You are worried for you are unable to disconnect with what is predominant in the mind. If a thought is predominant you are unable to disconnect from that, if an emotion is predominant you are unable to disconnect from that. When you are unable to disconnect, and you are caught in the swirl of those emotions and thoughts, then that is obsessive-compulsive behaviour.
From the perspective of the mantra, it is mananat trayate iti mantraha. Mantra is the procedure, the method which frees the mind from its own obsessive-compulsive thinking.
When you do the mantra, you are breaking this thought pattern and focusing your awareness and thoughts on something different. The first thought became the cause of your anxiety and worry. Then you cut that, and you generate a second thought which allows you to experience peace and harmony within you. That is the effect of mantra, for mantra realigns and reorganizes the energy structure of the body and mind.
Mantra is a whole subject mantra vijnana, the science of mantra. It is not called mantra vidya, knowledge of mantra. It is not the knowledge of mantra, but the science of mantra. Where the word 'vijnana' or the idea of science is used, it indicates a specific procedure that the mantra takes you through, which is sequential. There are various types of mantra in mantra vijnana. One is mantras like Om Namo Bhagavate Vasudevaya, Om Namah Shivaya, the Mahamrityunjaya mantra, the Gayatri mantra. These are common mantras or universal mantras, which anybody can use for a specific purpose.
Then there is the guru mantra which is personal and private. It is given to you according to what the guru wants: what level of understanding, what growth, what aim the guru wants you to achieve in life. Therefore, it becomes a personalized sadhana. If the guru gives the mantra So-Ham, you are free to do all the other mantras like Mahamrityunjaya, Gayatri, or various stotras, yet your personal sadhana is indicated by the mantra So-Ham. This mantra So-Ham, when you do it as a meditative practice and not as a chant, internalises you. The spandan or the vibration influences the behaviour of the brain. Your brain is relaxed and tranquillized.
—15 April 2014, Chembur, Mumbai, India