What is the most mysterious and profound secret that Krishna gives to Arjuna?

Krishna draws the distinction between sannyasa, or renunciation of selfish acts, and tyaga, or the renunciation of results-based action. Krishna says tyaga comes when you fulfill your obligations, knowing they are obligatory, but desiring nothing for yourself. True renunciation comes with the loss of desire for physical rewards.

In order to reach tyaga, a body must learn to master the body, the means, the ego, the performance of service, and the divine will. A saatvic worker will have no stress, because he is not bound by ego or self-will, and instead sees himself in service of a larger indestructible Being. He is free from egotism and selfish attachments, and full of enthusiasm and fortitude in success and failure alike, knowing he is part of the fabric of a larger consciousness.

Krishna asks Arjuna whether is he is now free from doubts and confusion and

Arjuna thanks him, agreeing that his faith is now firm and he will do his will. Sanjaya closes the Gita by saying that this was the supreme secret of spiritual union, directly from Lord Krishna, and that wherever he is, there will be prosperity, victory, happiness, and sound judgment.

bhakti is the sanskrit word for love and devotion.

atman is the Self or deepest part of the soul in every being that is often concealed by illusions, deceit and delusion.

dear friend,the most most mysterious n profound secret . delivered by LORDKRISHANA to arjuna,is ''yogi bhava arjuna...gita 46/06 and the secret of process being yogi".it was told to arjuna b'case he was dear devotee and birth to birth friend.