Wikipedia
Titiksha or titikșā ( Sanskrit: तितिक्षा) (literary the desire to leave) means the showing of forbearance to a person one is capable of punishing; in Vedanta philosophy it is the bearing with indifference all opposites such as pleasure and pain, heat and cold etc. It is one of the six qualities beginning with Sama, the repression of the inward sense called Manas.
Shankara defines Titiksha in the following words:
सहनं सर्वदुःखानामप्रतिकारपूर्वकम् | चिन्ताविलापरहितं सा तितिक्षा निगद्यते || "Endurance of all afflictions without countering aids, and without anxiety or lament is said to be titiksha." ( Vivekachudamani 25)By speaking of titiksha as endurance without anxiety or lament and without external aids, Shankara refers to such titiksha as the means to inquiry into Brahman, for a mind which is subject to anxiety and lament is unfit for conducting this kind of inquiry. Vivekananda explains that forbearance of all misery, without even a thought of resisting or driving it out, without even any painful feeling in the mind, or any remorse is titiksha.
The practice of Yoga makes a person inwardly even-minded and cheerful. The very act of calming emotional reactions develops a better ability to influence outer circumstances, therefore, titiksha does not make one apathetic or dull; it is the first step to interiorizing the mind, and to bringing its reactions under control. The important way of practicing titiksha is to watch the breath (parahara) which practice leads to the practice of meditation proper. Prakrti (matter or nature) shows the way to titiksha, the creative principle of life – just as inertia is a property of matter.