What is the obstacle to one-pointed meditation? The answer is the unstill mind. All problems are caused by the mind, by the desires arising in it. It is not easy to control the mind and keep it away effectively from desire. If we ask the mind to think of an object, it seems to obey us for a moment, but soon it takes its own course, wandering off. When I speak to you about meditation and tranquillity, for a moment your mind will perhaps become still and you will be happy. But in a trice it will go astray and the calm you experienced for a few seconds will give place to unquietness.
If you bid your mouth to keep shut, it obeys you for a brief moment. Similarly, if you close your eyes asking them not to see anything, they shut themselves off from the outside world for some moments. But try as you might to tell your mind not to think of anything, it will not listen to you.
The mind must be kept under control. Thinking and non-thinking must be governed by your will. Only then can we claim that it is under our control, that we are masters of our own consciousness.
Lunatics are usually referred to as people with no control over their minds. In fact none of us have any control over the mind. A madman keeps blabbering. But what about us? We let the mind go freely to keep blabbering inwardly.
Do you know what it means to have mental control? Suppose you are suffering from a severe pain. If you ask your mind not to feel the pain, it shall not feel it in obedience to you [that is you will not feel the pain]. Even if a tiger comes face to face with you and growls you will feel no fear if you ask your mind not to be afraid of the beast. Now we keep crying for no reason. If the mind is under control we will keep smiling even if there is cause for much sorrow. And under the gravest of provocations it will not be roused to anger and will remain calm.
First we must train our mind not to keep wandering. One way of doing it is to apply it to good activities. When oil falls in a steady flow, without spraying, it is called "tailadhara". The mind must be gathered together and made steady. It must be accustomed to think of noble and exalted objects like the Lord. Eventually, the very act of "thinking" will cease and we will dissolve in Isvara to become Isvara.
Yoga is controlling the mind in this manner.
Before we pass on, we must find a way to control the mind. Otherwise, we will be born again and we will be subject to the constant unquietness of the mind again. So we must use the opportunity of this birth itself to subdue the mind even while we are in the midst of so much that can rouse our desire or anger. A man who has succeeded in bridling his mind thus is called a "yukta" by the yogins. He is a "sukhin", one who truly experiences bliss, so says Sri Krsna
You must not turn away from yoga thinking that it is meant only for people like the sages. Who needs medicine? The sick. We suffer from manovyadhi, mental sickness. So we must take the medicine that cures it.
There are two different ways of mastering the mind- the first is outward (bahiranga) and the second is inward (antaranga). We must have recourse to both. The Matha has a cartman and a cook. Their work is outward in nature. Then there are those who prepare the wicks of the lamps, gather flowers for the puja - they are "inward" workers. Both types are needed for the functioning of the Matha. By employing both the outward and inward means, the mind must first be applied to good things one-pointedly and eventually lead to a state in which it does not think of anything at all.
The outward means consists, for example, of sandhyavandana, sacrifices, charity and so on. The best inward means is meditation. There are five inward(or antaranga) means to aid meditation. They are ahimsa(non-violence), satya(truthfulness), asteyam(non-stealing), sauca(cleanliness) and indriya-nigraha[subduing the senses, if not obliterating them]. To practise ahimsa is to imbue the mind with love for all and not even think of harming others. Asteyam means not coveting other people's goods. For satya, or truthfulness, to be complete one's entire being, including body, mind and speech, must be involved in its practice. Sauca is hygiene, observing cleanliness by bathing, maintaining ritual purity, etc. Indriya-nigraha implies limits placed on sensual enjoyment. "The eyes must not see certain things, the ears must not hear certain things and the mouth must not eat certain things"- restrictions with regard to what you can see, listen to, eat and do with your body. The body is meant for sadhana, for Atmic discipline. The senses must be "fed" only to the extent necessary to keep the body alive. These five dharmas are to be practiced by all Hindus without any distinction of caste or community.