The wise grieve neither for the living nor for the dead. There was never a time when you and I and all the kings gathered here have not existed and nor will there be a time when we will cease to exist.

As a caterpillar, having come to the end of one blade of grass, draws itself together and reaches out for the next, so the Self, having come to the end of one life and dispelled all ignorance, gathers in his faculties and reaches out from the old body to a new

For even if the greatest sinner worships me with all his soul, he must be considered righteous, because of his righteous will. And he shall soon become pure and reach everlasting peace. For this is my word of promise, that he who loves me shall not perish. -Krishna; Chapter 9, verses 30–31.

It is I who remain seated in the heart of all creatures as the inner controller of all; and it is I who am the source of memory, knowledge and the ratiocinativefaculty. Again, I am the only object worth knowing through the Vedas; I alone am the origin of Vedānta and the knower of the Vedas too. — Krishna; Chapter 15, verse 15

Perform all thy actions with mind concentrated on the Divine, renouncing attachment and looking upon success and failure with an equal eye. Spirituality implies equanimity.
[Trans. Purohit Swami]

You have the right to work, but never to the fruit of work. You should never engage in action for the sake of reward, nor should you long for inaction. Perform work in this world, Arjuna, as a man established within himself - without selfish attachments, and alike in success and defeat.