Harmony is called Yoga-Samatvam Yoga Uchyate,-says the Bhagavadgita. In spite of all scientific advancement, even today man continues to suffer as before, from the beginning of recorded history. This is due to disharmony within himself and with the world outside. Man is nothing but a part of Nature. And Nature is constituted and governed by the three Gunas, the fundamental entities, Tamas, Rajas and Sattva. The 'Gunas' here do not mean properties or characteristics. They are the substances out of which this universe manifests itself in its multitudinous forms. Tamas is said to be static. Rajas, dynamic, and Sattva a state which is neither and which transcends the two. The process of evolution also is carried on by these three Gunas. Evolution means creation and its progressive development. Its basis lies in activity. These three Gunas exist like the three strands of a rope supporting one another. But, one Guna always predominates keeping the other two under subjugation. Our body is predominated by Tamoguna. It is gross, inert and visible. Prana is predominated by Rajoguna. It is dynamic and we feel its existence due to the movements in our body. Mind is predominated by Sattvaguna. Our entire personality is nothing but the combination of body, Prana and mind. This combination we call 'I'. All our troubles are due to a disharmony among these three, the body, Prana and mind. It is this state of disharmony that puts man under the clutches of the three Gunas. A state of harmony frees him from their grip. Yoga brings about this harmony. It prescribes Asana (posture), Pranayama (regulation of breath) and Dhyana (concentration and meditation). Asana is for bringing about harmony in the body, Pranayama in Prana and Dhyana in the mind. The nature of Tamoguna is to check or retard, but it should not be thought that when the movement is upwards through Rajoguna, Tamoguna is absent. Any process however small it may be, needs a force to develop, another force to move it, and a third to check or maintain it. The force that develops is Sattvaguna, that which causes movement is Rajoguna, and that which checks or maintains is Tamoguna. No one Guna exists in isolation without the influence of the other two. A lotus kept in a pot of water is disturbed when the pot is distrubed. The disturbance of the pot is transmitted to the water which in turn transmits it to the lotus. Similarly, any disturbance to the body is carried to the Prana, which again communicates it to the mind. To keep up the stability of our whole personality, Yoga prescribes Asana, Pranayama and meditation.
Sages emphatically declare that Yoga alone can destroy all pains. Yogo Bhavati Duhkkaha- Yoga is the destroyer of pain-says the Bhagavadgita. There are many definitions for Yoga. Merely memorising them and repeating them will not produce the desired result. Instead, we have to put it into practice in our daily life. If one understands the principles and applies them in one's day-to-day activities, life itself becomes a process of Yoga, and Yoga is the destroyer of pain.
Practice of Yoga creates harmony in the physical, vital, mental, psychological and spiritual aspects of the human personality. Different limbs constitute the human body. Similarly, there are a number of limbs in Yoga. They are mainly classified under eight heads: Yama (moral restraints), Niyama (spiritual observances), Asana (posture), Pranayama (regulation of breath), Pratyahara (withdrawal of mind from external objects), Dharana (concentration on one object), Dhyana (meditation), and Samadhi (Supreme Harmony). If a person moves one step forward, all the limbs of the body also move simultaneously. Even so, if one practises even one limb of Yoga to a high degree of perfection, all the other limbs of Yoga are bound to accompany without great effort on the part of the practitioner.
When one desires to practise Yoga Asanas, one should naturally have externally congenial, conducive atmosphere. This can be brought about by observing Yama, viz., Ahimsa (observance of non-injury through thought, word and deed), Satya (truthfulness), Brahmacharya (all-round self-control), Aparigraha (non-acceptance of free gifts which are not essentials), Asteya (non-stealing). One should not practise Yoga Asanas when the mind is disturbed due to fear, anxiety, fatigue or tiresomeness. These can be overcome by the practice of Yama. An external congenial atmosphere alone is not sufficient. There must also be the internal serenity of mind. This is obtained by the practice of Niyama. This constitutes Saucha (internal and external purity), Santosha (contentment), Tapas (austerity), Svadhyaya (self-study) and Isvarapranidhana (surrender to God). Thus Yama and Niyama are two important unavoidable prerequisites for the practice of Yoga. The third and fourth limbs of Yoga are Asana and Pranayama. During the practice of Asanas there should not be any rapid movements of the limbs of the body or jerks of the body. By this, the breathing process is regulated automatically. While doing the Yoga Asanas, the mind should not think of the programmes and engagements of the day or any other external object. One must withdraw the mind from all such thoughts. This is called Pratyahara, the fifth limb. Here, a question may arise: On what should one direct the mind, when it is withdrawn from external thoughts, for its very nature is to go outward? Hence, it is suggested by the adepts that while doing Asanas, one should concentrate one's mind on the relevant parts of the body according to the nature of the Asana practised. Keeping the mind on a particular object for a short time is Dharana or concentration. Continuous concentratiion, on the object for a long time is called meditation. "Pratyaya Ekatanata Dhyanam." Thus when all the seven limbs of Yoga are brought in, the eighth limb, Samadhi or Supreme Harmony results as a natural sequence. The practice of Yoga Asanas thus leads to this Supreme Harmony.
Even though the ancient sages have named several postures with the appellations of reptiles, birds and animals with which they had some resemblance, only human beings can practise Yoga Asanas, combining with them the eight limbs of Yoga, but not the other beings. Merely bending the body cannot constitute Yoga Asanas. In Yoga, there should be a blending of all the eight limbs. Hence, Sage Patanjali said: "Yoganga Anushthanad Asuddhi-kshaya Jnana-diptir Aa viveka Khyateh-By observing the eight limbs of Yoga, one effects the destruction of impurities, then arises spiritual illumination which leads into awareness of the Reality." This is the supreme purpose for which the practice of Yoga is recommended.