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]

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.

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.

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

The little space within the heart is as great as the vast universe.
The heavens and the earth are there, and the sun and the moon and the stars. Fire and lightening and winds are there, and all that now is and all that is not.

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.