Titikṣā is endurance. Cold and heat, joy and pain come and go, and Kṛṣṇa tells Arjuna to bear them. The original “this too shall pass”.
Going deeper
2.14 is where Kṛṣṇa tells Arjuna what to do with feelings. Contact between the senses and their objects gives rise to cold and heat, pleasure and pain. They come and go and do not last. Endure them, he says, and that instruction is titikṣā. The verse before, 2.13, had said that the self passes through childhood, youth and old age in this body and then into another, and that a wise person is not deluded by that. 2.15 says that the one whom these do not disturb, who stays the same in pain and pleasure, is fit for immortality. So the case for endurance rests on impermanence: what comes and goes is not worth being unsettled by. The story calls it the original this too shall pass. The passage is in chapter 2, and what the Gītā says about grief gathers related verses.