Endurance and austerity are preconditions to a spiritually elevated life. Both of these are related, in one way or the other, with several kinds of afflictions. Illness or injury is an affliction. Jealousy, emotional imbalance, hatred, etc., are also the sources of affliction. You should be ready to face these afflictions, as they are, without succumbing to any illusions about them. To endure them with this attitude is called endurance (titiksha). When you accept or face them as different phases of your sadhana, thinking that they make you learn a lot and add to your experiences, then it becomes your tapasya, or austerity.
To expose oneself willingly to uncomfortable situations or conditions (which is commonly called self-torture), should not be discarded as something irrelevant. Many people do tapas, standing on one leg or with their head down on the ground or amidst the fire flames or neck deep in icy cold water. It destroys their tamas. This is titiksha. To accept these situations, in the spirit of a sadhaka, is tapasya.
Titiksha is not only torturing the body. It is torturing the mind also. Kabir said to keep your enemy in your close proximity. Let him be housed properly. He will 'wash' your temperament without soap and water. It means that you should not shun those who abuse you, censure you or are jealous of you. It is not enough that you have enemies for this purpose. You should, literally, live amongst them. They will strengthen the weak points in your personality. This attitude is called titiksha.
You may be loving a person intensely. You may be restless without him or her. Yet, with full consciousness of what you are doing and thinking, you keep yourself at a distance. A devotee calls out to his deity only from a distance. This is titiksha. But if the circumstances have separated you from your friend, this is not titiksha. To expose yourself wilfully and gladly to an adverse circumstance or situation and to 'live' it- is titiksha. To accept such a situation ungrudgingly as a part of sadhana, is tapasya. Tapasya is not merely facing a situation helplessly, simply because there is no other way out or it has been imposed on you. It is not just weeping in unfavourable circumstances and being happy in favourable situations.
Tapasya and titiksha endow the sadhaka with siddhis, often very soon. Many people go to Vaidyanath Dham in very inconvenient postures counting their steps and synchronising them with recitation of mantras. What does it result in? They are bestowed with the siddhi of patience. They get it without any effort. This effortlessness, which is akin to the state of spontaneity, comes when physical discomforts are being ignored. Even while running a high temperature, your mind may be established in a state of void. It may harbour nothing- neither love, nor anger.
To overvalue or overestimate afflictions leads to more afflictions. However, when you expose your body to discomforts for a long time and ignore them mercilessly, then they lose their power over you. In this state of void, the chakras in your body are opened and siddhis are bestowed. It must be noted, however, that if you have attained this point in sadhana to achieve an end, you will not get any siddhi - only your desires will be fulfilled. To be guided by any personal motive disqualifies you from obtaining the treasure of siddhis.
It has been observed that people practise their sadhana with a resolve (sankalpa) to get some material gain. Many scientific devices and other means can be exploited for materialistic achievements. Your resolves should not be a replacement for those devices and means. Let your sadhana not be nullified by such resolves. Materialistic needs should not be allowed any place in your spiritual efforts. Such requirements can be fulfilled without much difficulty. You can get money and home; you can earn name and fame, even if you do not possess them, through your personal efforts. But do not try to get these material gains through your resolve. The resolve is meant for fulfilling higher purposes. The power of resolve- or the willpower- should be preserved very carefully to make full use of the divine grace which will be bestowed upon you as a result of your sadhana or austerity.
I am reminded of an example here. Dushshasana was dragging Draupadi to the royal court to undress her. Poor Draupadi first looked for help to the elders sitting there- her husbands, Dhritarashtra and many others. Seeing not a single ray of hope for her protection, she directed her entire willpower towards Lord Krishna. Whether or not Lord Krishna presented himself physically in the royal court is not as important as the fact that the willpower of Draupadi yielded marvellous results. Dushshasana was continuously pulling Draupadi's sari off her body to undress her. And he became exhausted! Draupadi did not use her willpower simply to protect herself from being undressed. She wanted to show everybody that the power of resolve alone, could certainly draw down the forces of God. She wanted to tell the Kauravas that through such a resolve anything can be achieved without waging wars: even the grace of God can be made to descend to earth. This example elucidates how through the power of her austerity Draupadi could actualise her resolves.
The power received through practising austerity and endurance should be aimed at one and only one divine goal - self-realization or God-realization. You should understand that titiksha is a noble quality to be practised. A word of caution for the indolent- you should never be tempted to exempt yourself from doing asanas, pranayama, japa, etc., on the pretext that you are already practising titiksha, a more powerful form of sadhana. Titiksha is not just a show. What, after all, makes you sure that you are really practising titiksha and not just facing certain afflictions helplessly due to the pressure of circumstances?
Many people have recently come to yoga. Therefore, they must practise asana, pranayama, meditation and concentration - and develop titiksha and tapasya.