Are you angry? Who is the enemy that provokes your rage today? In the famous comic strip Pogo observed to his friend Porky Pine, "We have met the enemy and he is us."
Paul knew that Christians are in a great battle. It would have been easy to demonize other people -- the Roman Government, the Judaizers, their own family members. But Paul said, "Our struggle is not against flesh and blood..." The real enemy is the organized force of evil in the universe. We cannot always see our enemy but he is always at work, creating strife.
There are two dangers when it comes to the devil: to deny his existence and to give him too much credit. To say that we fight against spiritual forces of evil is not to deny our personal responsibility for our choices. We can be our own worst enemies. But where there is hatred, envy, strife, lust, abitterness, we may be sure that an enemy has planted the seeds. Whatever we do, we must not water those seeds. They need no nurture from us.
Remember the novel This Present Darkness? Author Frank Peretti painted a picture of the way spiritual forces of evil might be at work in the world unseen by us. The one weapon which worked against the enemy was prayer. To be clear, I do not see a demon in every bush. But I believe that a personal force of evil works against us. So put on the full armor of God. Use the sword of the Spirit which is the word of God. By all means pray.