Q: Titikṣā kā? What is titiksa? A: Śītōṣṇa-sukhaduḥḵẖādi-sahiṣṇutvaṁ I
It is endurance of cold, heat, pleasure, pain, etc.
When we are talk about endurance, it does not mean only putting up with the object or situation which is unpleasant. It is not merely putting up and suffers. If I put up with it outwardly, but resist inwardly, is not titiksa. Titiksa means the ability to put up with unpleasant without suffering. Ofcourse when there is change to improve the situation, one should go ahead and do it. But the most important is to develop the poise of mind while one in the situation which can not be changed upon. These situation is our life.
Life is consist of pair of opposite. Birth and death, hot and cold, up and down, pleasure and pain. Everything is potential to manifest in total opposite, and potential to give pleasure and pain. Anything which has birth for sure will have death. It is just the matter of time, these pairs of opposite will manifest. What is my object of pleasure will become object of my pain. Therefore this entire Jagat-world is called mithya-can not be categorised as real or unreal. The happiness I got from particular object or situation was so real, why it is no more there. Either the object or the situation is not there all the time to bring us happiness, or happiness is no more there even though the same object or situation is there. Therefore this world is called Jagat (gatchati gatchati gatchati iti jagat - that which is moving / changing is called jagat).
The final titiksa is seeing the mithyatvam-status of being impermanent of this transactional world which is nothing but the contact of sensory organs and sensory world which given rise of cold-heat, pleasure-pain. Therefore these pairs of opposite also subject to coming and going. I don't see them being real. I am the only reality which is the seer of the unreal. In Gītā, Srīkrsna said:
mātrāsparśāstu kaunteya śitosnasukhaduhkhadāh I
āgmāpāyino' nityāstāmstitiksasva bhārata II 14 II
Kaunteya (Arjuna)! The contacts of the sense organs wit the sensory world that give rise to cold and heat, pleasure and pain, which have the nature of coming and going, not constant. Endure them, Bhārata (Arjuna)!
yam hi na vyathayantyete purusam purusarsabha I
samaduhkhasukham dhīram so' mrtatvāya kalpate II 15 II
Arjuna, the prominent among men! The person whom these (sukha and dukha) do not effect, who is the same in pleasure and pain, and who is discriminative, is indeed fit for gaining liberation.
nāsato vidyate bhāvah nābhāvo vidyate satah I
ubhayorapi drsto' ntah tvanayostattvadarśibhih II 16 II
For the unreal (mithya), there is never any being. For the real, there is never any non-being. The ultimate truth of both (real and unreal) is seen by the knowers of the truth.