In Chapter 10, Arjuna wants to know how to keep in touch with the Eternal Truth, while perceiving the pluralistic world and transacting with it. This Chapter abounds with examples of the joyous Infinite among the joyless finite objects.
In Chapter 11, Lord Krishna shows Arjuna a vision, wherein he sees the entire universe compressed in the Krishna's form. Arjuna is thus completely converted both in his faith and understanding. Having had vision of Lord's form, Arjuna is overwhelmed with devotion. He wants to know what are the characteristics of a great devotee which he should develop.
So in Chapter 12 & 13, Sri Krishna talks about the qualities of a devotee.
In Chapter 14, Lord Krishna explains the three gunas - sattva, rajas and tamas, how they affect man's life and how man can rise beyond them.