This may seem like a strange place to start, but you should know that I am a movie fan.  I love all sorts of movies.  And just about every movie that I can think of provides something of an answer to this question.  I am also something of a reader and it seems that most of the literature that I enjoy also provides something of an answer to our question.  From the cartoons that I loved as a kid, to the books that I read to the movies that I watch, one of the most enduring stories of all time involves the ageless battle between good and evil.  God Versus Satan, Popeye versus Bluto, the Allies versus the Axis, the quiet kid in the back of the class versus the bully, you get the idea; all of life is engaged in the struggle of Good versus Evil. 

Often we don’t like to think in such black and white terms, and indeed sometimes it is difficult to figure out just who is on the side of Good and who is on the side of Evil.  But that too is a part of the “never-ending story”.  When we simplify, or over-simplify the stories it is easy to tell who is the bad guy (he is wearing a black hat) and who is the good guy (he is wearing a white hat).  The reality is a good bit more sticky.  The cartoons depict the Devil as the one in the red suit with the horns and the pointy tail carrying a pitchfork.  The reality is a good bit more difficult.  When he appears, the Devil will likely be very good looking, have a calm, clear, and soothing voice, and he will present us with some very attractive opportunities.  I’m a fisherman.  Every time I go fishing I play the part of the Devil to the fish.  I present them with some very attractive tidbits in order to entice them to bite.  Unfortunately for the fish, I always include a hook with my bait.  So does the Devil.

The quote that was given with the question is a part of the Bible’s answer to the question.  In short, all of life is a struggle of a sort of warfare, spiritual as well as temporal.  Every struggle that you and I engage in has a definite spiritual dimension.  That disagreement that you just had with your wife has human sin as an element.  That temptation to eat the last donut is a battle between your carnal desires and what you know is the right thing to do.  That is the point of Paul’s great discussion of the battle between good and evil.  Read that brief few verses from Ephesians right now:

Eph 6:10-20

10 Finally, be strong in the Lord and in the strength of his might. 11  Put on the whole armor of God, that you may be able to stand against the schemes of the devil. 12 For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. 13 Therefore take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand firm. 14 Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness, 15 and, as shoes for your feet, having put on the readiness given by the gospel of peace. 16 In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one; 17 and take the helmet of salvation, and the sword of the Spirit, which is the word of God, 18 praying at all times in the Spirit, with all prayer and supplication. To that end keep alert with all perseverance, making supplication for all the saints, 19 and also for me, that words may be given to me in opening my mouth boldly to proclaim the mystery of the gospel, 20 for which I am an ambassador in chains, that I may declare it boldly, as I ought to speak.   ESV

We should know that we cannot prevail in our battle relying on our own strength.  The Devil is much stronger than any human force, so we must draw on the strength of the Lord.  We must equip ourselves for the battle with the weapons of Truth, Righteousness, Readiness, Faith, trusting in our Salvation, and strong in the knowledge of the Word of God, Alert, always Prayerful, and leaning upon the Holy Spirit.  This is our daily battle and these are our daily tools, and our daily bread.