In the Fifteenth Chapter, fifteenth verse, you'll see, Kṛṣṇa says that "I am sitting in everyone's heart." Sarvasya: not only human being, all living entities. Not only living entities, even in atom, within the atom, He is present there. Sarvasya.
Sarvasya means everything, the Supersoul. Sarvasya ca aham Kṛṣṇa. Kṛṣṇa says: "I," hṛdi, "in the heart." When it is called hṛdi, that means living entity. Without living entity, there cannot be any heart. Without this body, no, there cannot be any heart. In the stone there cannot be any heart. Dead body. The heart is dead.
So sarvasya ca ahaṁ hṛdi. Hṛdi means "in the heart." Sanniviṣṭaḥ: "I am situated. I am sitting there." And mattaḥ smṛtir jñānam apohanaṁ ca (BG 15.15).
Because He is sitting there, therefore all kinds of remembrance, smṛti, knowledge and forgetfulness. These things are functions of the mind. You remember something, you gather some knowledge, and sometimes you forget. "Let me think. Oh, yes. I forgot, yes." That's a function of the mind.
So that forgetfulness is also due to Kṛṣṇa, because He's sitting there. He's guiding. If you want to forget Kṛṣṇa, He'll give you so opportunity of māyā that you can . . . you'll never remember Kṛṣṇa. You'll forget for good.