Arjuna's collapse comes in an order. The body gives way first (1.29-30), then his sense of what victory is worth (1.31-35), then his reasons (1.36-44), and at last the reasons turn on him (1.45-47).
The closing chapter names the book three ways. It is a dialogue (18.70, 18.74), a secret yoga heard first hand (18.75), and a teaching whose study is an offering (18.70).
These verses are spoken inside a vision, to one person, at the edge of a war; the Lord takes away Arjuna's claim to be the author of the outcome and his fear, not his action (11.32-34).
The promise rests on one whole turning, not on the past: a person of very bad conduct who worships with undivided devotion is to be regarded as righteous, because he has resolved rightly (9.30).
Offering is the practice that carries the knowledge 'I am not the doer' into the middle of work. The person goes on working; what is handed over is the claim 'this is mine and I want its fruit' (3.30).