Summary: In the Spiritual battle we fight every day, sometimes the worst enemy we face is ourselves, our sinful nature.
We are in a battle. Every day, every hour, every minute. As we had already studied:
Ephesians 6:12 (NASB95) For our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the heavenly places.
Last week we looked at the devil, but we as Christians must realize that the devil may affect circumstances around us, the devil may tempt us, but the devil cannot make you do anything. It is our flesh that is weak. It is our sinful nature.
In his book, Being the Body, Charles Colson writes, “What Oprah is preaching is not particularly new. It’s just that the combination of her public access and immense influence, as well as the particular appeal of her own earnest search for meaning, make it uniquely twenty-first century. The Church of O encourages people to ask all the right questions about life, meaning, service to others, identity—and then to look in precisely the wrong place to find those answers. Within.”
Unfortunately, the answers aren’t within—that’s where the problem lies. We’re all sinners—not Saviors. The answer is outside of ourselves. We don’t need personal reflection; we need a Savior. One who can forgive us and save us from our sins. 
Answers to life are not found within. That's clearly the wrong place to look. The Bible clearly states:
Jeremiah 17:9 (NASB95) “The heart is more deceitful than all else And is desperately sick; Who can understand it?
Today we will look at the battle we face every day. The enemy is within – our flesh. The fact is for most of us, in living the true Christian life, we are own worst enemies.
A man who strolled out of a hardware store with a smile on his face and a brand-new chainsaw in his hands. He was told it could cut down five big oak trees in an hour. Twenty-four hours later, however, his smile was gone. Frustrated, he was back at the store complaining that the saw would never cut five trees in an hour. "It took me all day to cut down one tree." Puzzled, the store owner stepped outside with the saw, gave the cord a swift pull, and fired up the steel-toothed beast. Its deafening roar sent the customer stumbling to get away. "What’s that noise?" he gasped.
This is exactly how most Christians try to live. Claiming to have the Holy Spirit but never filled with the Spirit’s power or trusting in the Spirit. The fact is, life is a struggle: A struggle physically. A struggle emotionally. A struggle Spiritually.
Our war is not against physical things, but against evil in heavenly places. We have many foes in this battle, the first we have to contend with is ourselves. As stated earlier, often we are our own worst enemy.
Galatians 5:16 (NASB95) But I say, walk by the Spirit, and you will not carry out the desire of the flesh.
The lust of the flesh. What exactly is that? The fact of the matter is we have a sinful nature. We got this sinful nature at birth. We inherited it all the way from Adam. It is in our genes – it is genetic. We are faced with the lust of the flesh or said another way, our sinful nature. Paul is telling the church in Galatia that they must walk in the Spirit to avoid succumbing to that sinful nature.
Galatians 5:17–18 (NASB95) 17 For the flesh sets its desire against the Spirit, and the Spirit against the flesh; for these are in opposition to one another, so that you may not do the things that you please. 18 But if you are led by the Spirit, you are not under the Law.
This is the problem: There are two natures in the believer (I am preaching to Christians here). And they are at war with each other. The Spirit and the flesh–our sinful nature, in constant conflict. Then throw in temptation form the devil for good measure. This spiritual battle rages inside of us. Paul thoroughly understood that. He wrote much concerning that conflict between the Spirit and our sinful nature.
Romans 7:15–21 (NASB95) 15 For what I am doing, I do not understand; for I am not practicing what I would like to do, but I am doing the very thing I hate. 16 But if I do the very thing I do not want to do, I agree with the Law, confessing that the Law is good. 17 So now, no longer am I the one doing it, but sin which dwells in me. 18 For I know that nothing good dwells in me, that is, in my flesh; for the willing is present in me, but the doing of the good is not. 19 For the good that I want, I do not do, but I practice the very evil that I do not want. 20 But if I am doing the very thing I do not want, I am no longer the one doing it, but sin which dwells in me. 21 I find then the principle that evil is present in me, the one who wants to do good.