People usually think that yoga means no more than controlling the breath and sitting stone-like. The literal meaning of the word is "joining", "uniting". All through our life's journey we have to join ourselves to various objects. But such joining is no permanent. That is why the mind remains unsteady. If we are joined to an object without the least possibility of being seperated from it, it is yoga in the true sense. The root of the minds of all of us is the one Paramatman. Yogins control their breath to turn their mind to this prime root object. The root that gives rise to thoughts is the same as the root that gives rise to the breath. So if the breath is fixed on the root, the mind too will be absorbed in it.
The opposite of yoga is "viyoga". When the man dies we say that he has attained viyoga. The Lord says in the Gita that a particular kind of viyoga is itself yoga. What is it? If you keep away sorrow, that is if sorrow does not attach itself to you, you have the yoga of disconnection(Tam viyad dukha-samyoga-viyogam yoga-samjnitam. )
What we normally understand to be pleasure in a worldly sense is truly sorrow. All experiences that creates separation from the Paramatman are sorrow. It is because the citta or consciousness is unstill that we undergo sorrow and happiness. These disappear when the mind is still. To make the mind pure it to train it in one-pointedness. This is the mean of yogic perfection. To start with, all will be able to control their breath like yogins. If we are absorbed in a worthy subject, in some good work, our mind will remain untainted to some extent. If we try to control our mind in one go, so to speak, it will free itself and wander in all directions. If we keep doing some noble work or take an interest in some noble subject the mind is less likely to become unstill.
In the old days they used to wear what is called an arikandam, that is an iron ring, round the neck to keep themselves disciplined and live according to the sastras. In the same way we must wear an arikandam to keep the mind from going astray. To be involved in good actions is itself a kind of arikandam.
Performing sacrifices, observing fasts and vows, building great temple towers, digging ponds, etc, were a means in the past to cleanse the mind by making it one-pointed. In the midst of such good work also one experiences difficulties, even humiliation, but one should not be daunted by criticism or obstacles. This itself becomes the means of mental purification. Then come pranayama, meditation, etc.
The kazhakkodi keeps rolling without gathering any dirt. If you smear some ashes on it they will not stick to it. Like the kazhakkodi we too must not be affected by pain or pleasure and keep journeying towards the Paramatman and becoming one with It. Such union is called yoga - it is our original as well as ultimate state. In between we somehow become different. That is why we do not understand that ultimate and original state now. To reach that state we must make a beginning with the performance of rites.
For a general background, please see here