The modern idea of desire says that our desires are basically good. We want food, drink, clothing, sex, friendship ' 'good things' ' we just need to make sure that we pursue our desires in a 'healthy' way. In other words, the modern world agrees with the Gentiles. Pursue your desires ' 'follow your heart' ' just use wisdom in seeking the things that you desire.
Jesus says, No. Do not be like the Gentiles. Do not follow your desires. Follow me.
So when James warns us against our desires ' he is not a killjoy. He is opening the only path to joy!
The way of faith. Will you believe God? Will you trust him? Will you listen ' will you hear what he is saying? And then will you do it?
Because that is the test of genuine faith. If you believe God, then you will do what he says!