The Bhagavad Gita is divided into three sets of six chapters. Chapters 1 to 6, 7 to 12, 13 to 18 are supposed to establish the identity of you and God. That's often people make this mistake about non-duality - that's why the dualistic schools of Adanta charge us with blasphemy. We are Brahman, but we don't know it to be so. And our whole purpose, whole goal is to become enlightened to this ultimate reality about ourselves, that we are Brahman.