The Oath and Covenant of the Priesthood

Serious comment: I have never really understood what the Oath and Covenant of the Priesthood actually is. (For those needing a reminder, it’s a half-dozen or so verses in Doctrine & Covenants sec. 84.) I understand the beginning (you do good) and the end (you inherit eternal life), but I don’t get the middle—how does getting from A to B work? And here’s what feels like everybody else in the church, blithely talking about the Oath and Covenant of the Priesthood like what it’s talking about is a simple given—and so I feel like I’m missing some blatantly obvious thing. So what is it, then? (Not to mention that it talks about living up to “this” oath and covenant, while I can’t figure out where exactly the antecedent is.)