Of course everyone has a particular relationship with the Lord, and that relationship is evoked by the perfection of devotional service. But in the present status of our life, not only have we forgotten the Supreme Lord, but we have forgotten our eternal relationship with the Lord. Every living being, out of the many, many billions and trillions of living beings, has a particular relationship with the Lord eternally. That is called svarūpa. By the process of devotional service, one can revive that svarūpa, and that stage is called svarūpa-siddhi—perfection of one's constitutional position. So Arjuna was a devotee, and he was in touch with the Supreme Lord in friendship.
How Arjuna accepted this Bhagavad-gītā should be noted. His manner of acceptance is given in the Tenth Chapter (10.12-14):