Kṛṣṇa calls Arjuna Guḍākeśa, the conqueror of sleep. In chapter 10 he uses the name again: I am the Self, O Guḍākeśa, in the hearts of all beings. The one who never sleeps is told where to look.
Going deeper
The first item in Kṛṣṇa's list in chapter 10 is a verse about the heart. In 10.19 he promises to speak of his most prominent glories, because there is no end to their extent. Then 10.20 begins: I am the Self, Guḍākeśa, dwelling in the hearts of all beings, and I am the beginning, the middle and the end of all beings. Guḍākeśa is a name for Arjuna, and the story reads it as conqueror of sleep. The verse is the one the story points to: the person addressed by this name is told where to look. 10.21 then moves outward at once, to Viṣṇu among the Ādityas and the radiant sun among lights. So the list starts by pointing inward and goes on into the world. See chapter 10, and what the Gītā says about knowledge collects related verses.