The word tapasya is often translated as austerity, but etymologically, tapas means a process of purification by which you make yourself more seasoned, more mature. The body of man is very weak, and his mind is weaker. When you have a weak mind and body, how can you complete your pilgrimage of life? When your motor car is not working properly, then it has to be sent to a mechanic. In exactly the same way, the body and mind have to be overhauled, and that process is known as tapas.
Many people think that tapas refers to the austere life of a puritan. Well, it is not a matter of logic or dispute. When your house is collapsing, either you repair it or move out. Now, this body is composed of different organs, processes and laws. If your digestive system is weak, can eating less be considered an austerity? No. In the same way, if you are indulging in sensual life and have too many attachments which are affecting the mind, heart and body, are you going to add more enjoyments, more attachments, or minimize them? When the body is sick, you have to maintain certain restrictions, prohibitions and abstentions. That is not austerity; it is a method of treatment, whereby you can purify and free yourself of the dirt, patterns and complexes that cause pain and suffering.
Tapasya is threefold. The highest form is sattvic tapas, which is intended to purify the mind and body for self-realization. Sattvic tapas has a spiritual purpose, and if you want to follow it, then you have to practise meditation. In meditation, when your mind is giving you a lot of trouble, then you must practise pranayama. The breath and mind are interconnected, therefore, pranayama is a very powerful method of controlling the mind.
Pranayama is an important form of tapasya. When you practise pranayama, yogic heat is created. This heat or fire of yoga helps in the awakening of kundalini. When the mind is possessed by the powerful force of kundalini, it becomes totally stable. This is sattvic tapas, a process whereby you generate physical heat in your body. This heat is vitally important for meditation, but if you practise pranayama without preparation, it will not fulfil this purpose.
Of course, everybody can practise pranayama, but for awakening kundalini you need to make a lot of preparations. You will have to practise asanas, bandhas and mudras, otherwise you will have difficulty in pranayama. The heat which is generated cannot be directed to the proper centres. Therefore, jalandhara bandha, uddiyana bandha and moola bandha are practised to lock the prana from all sides. In order to practise these bandhas correctly, the practice of asanas is very important. Therefore, we can say that all of hatha yoga is sattvic tapas.
Rajasic tapas is practised by continuous fasting and exposing the body to the elements of heat and cold in order to dissipate desires and attachments. This type of tapas usually causes repression, therefore, it requires understanding. Most people who practise this type of tapas, which can rightfully be called austerity, do not have a clear purpose and often do not even know why they are fasting. Therefore, the benefits are minimal.
The third type of austerity is called tamasic tapas. This is practised by forcing the body, which thereby affects the mind. For example, in India there are people called fakirs who place their body in a certain position and remain like that without moving for years on end.
Conclusively, those people who want to realize higher consciousness should practise sattvic tapas, but at the same time, it is important to avoid excesses in life. Excess makes the senses weak, when you should be maintaining a balance. Many people completely dedicate themselves to sensual life, thinking that even in a luxurious situation, self-realization can be obtained. Those who live in luxury weaken their bodies and minds because they are dependent upon sense objects.
Through tapasya, you are trying to set in motion a process of metabolism, by which all the habits that create weakness and obstruct the awakening of willpower, can be eliminated. You must know what your necessities are. Your life has to be made simpler. You have to make a choice, that's all. You can't have your cake and eat it too. Either you want samadhi or you want sensual life. To some extent you may be able to continue, but there comes a moment when you will have to make a departure from sensual life.
That is why tantra is practised. Its purpose is not to indulge in drinking, meat eating or sexual life, but to transcend your addictions. This is an important aspect of spiritual life. Mind is a very good advocate; it always argues for the senses. But in fact, even if you let your senses run riot, that doesn't bring you happiness. So it doesn't matter what the mind says. Go on with your tapas.