If you don’t know what the problem is, you’ll never come up with an answer. I sense that a lot of believing Christians don’t understand why their life in Christ lacks the joy they understood would accompany faith. It seems that life has declared war and all they wanted was peace. But wait – that’s exactly what has happened. Before faith we were relatively comfortable with the world in which we found ourselves. We understood that some things were right and other things were wrong, but in general we felt ourselves at home in a world that required no deep moral commitments.
But when we said Yes to the God who revealed himself in the person of Jesus Christ, a war broke out. Peter writes to his friends telling them to abstain from sinful desires that “wage war against your soul” (2:11). Well, there’s the problem – we’ve gone to war! Now the enemy in this war is not the world in which we live. Our opposition comes not from without, but from within. The enemy is sinful desire, and that is something we provide. Jesus lists twelve different “evil thoughts” that come from within and defile a person (Mark 7:21-22). So our war is a “civil war” – the worst possible kind! It is our old nature that attacks our soul (Greek, psyche, “the seat and center of the inner human life in its many and varied aspects” - BDAG).
Now that we understand who the enemy is – “the disordered natural inclinations” as the NLT put it – how do we do battle against them? How do we resist the very things that our own natural desires want us to do? It is helpful to understand that when we turned to Christ in faith we were granted a new spiritual life. That new life is empowered to resist successfully the demands of the old nature, but we are the ones who must constantly make the decisions. In every attack by the old nature we must decide to allow the available power of new life in Christ to rout the enemy. It always works! Someone put it this way. In each of us are two dogs, one black one white, always fighting. Which one wins? The answer is simple; the one we feed! So feed your spiritual life and you will win every skirmish against the old nature.