To wage good warfare as Christians, we need encouragement (from God's word), the right equipment (faith and a good conscience), and knowledge about our enemies (how they became enemies, where they're headed, and the hope for them) if we hope to succeed.
Paul won’t spend much time in this letter explaining how God saved us. He gives more attention to that in his other letters. But the understanding that underlies this whole letter is that we have a God who saves – a God who speaks for our good. And that explains why we listen to his voice, with trust and with joy...
Very few of us need encouragement to watch out for ourselves. But to watch out and pay attention to the needs of others, just as intently – that’s a challenge. That’s not natural. Indeed, it’s divine.