In the garden of Eden, Eve ate the fruit of the tree of the knowledge of good and evil so that she would be like God –able to decide what was right and wrong for herself and everyone around her. As her children, we are all that very same way –opinionated and judgmental –gods of our own ways.
The flesh (or sin nature) desires what is pleasing to the senses. The aroma of a favorite food stirs a craving that grows in our mind –often enhancing the expectation of that food's taste beyond what it can possibly fulfill. The same is true for each of our senses. We are sensual beings. Our senses draw our attention to the things of this world that we do not already have: more education; a better job; new clothes; a bigger dwelling; more food; a shinier car; less demanding relationships; compassionate friends; children that are more respectful; a kinder, prettier, sexier and more accepting mate...
Even as Christians, sensual desires never leave us –not as long as we live in this world. It's normal, common, natural, for us to want to fulfill these desires. That's an inseparably part of who we are as human beings. When combined with the fact that we decide what is right or what is fair for us to have in life (inherited from Eve), our emotions clearly reveal that fallen, sensual nature. Desires that are not satisfied cause us to feel hurt, disappointed, rejected, frustrated, angry –and above all we are anxious in anticipation of what will happen next. The flesh is always worried about not getting its way –having what is good for us –having what we rightly deserve.
Up to this point we have looked at how the law entices us to sin. But taking the law away does not take away the desire to sin –to fulfill the desires of the flesh– and reap the associated emotions and anxieties.
Sin naturally lives in our flesh –like glowing embers smoldering within us– and the law is like gasoline. Attempting to follow the law corresponds to pouring that explosive fuel onto the embers. The result is disastrous and predictable –we all have experienced them time and time again. Paul talked about it in Romans 7.
I do not understand what I do. For what I want to do I do not do, but what I hate I do. And if I do what I do not want to do, I agree that the law is good. As it is, it is no longer I myself who do it, but it is sin living in me. I know that nothing good lives in me, that is, in my sinful nature. For I have the desire to do what is good, but I cannot carry it out. For what I do is not the good I want to do; no, the evil I do not want to do—this I keep on doing. Now if I do what I do not want to do, it is no longer I who do it, but it is sin living in me that does it. (Romans 7:15-20)
Therefore, there is now no condemnation for those who are in Christ Jesus, because through Christ Jesus the law of the Spirit of life set me free from the law of sin and death. For what the law was powerless to do in that it was weakened by the sinful nature, God did by sending his own Son in the likeness of sinful man to be a sin offering. And so he condemned sin in sinful man, in order that the righteous requirements of the law might be fully met in us, who do not live according to the sinful nature but according to the Spirit. (Romans 8:1-4)
So from now on we regard no one from a worldly point of view. Though we once regarded Christ in this way, we do so no longer. Therefore, if anyone is in Christ, he is a new creation; the old has gone, the new has come! (2 Corinthians 5:16-17)
Although our thoughts can seem to be on many things at once, the fact is that we can only think about one thing at a time. Our minds merely jump from one thought to another in rapid succession. But by submitting to God's ways –as new creations in Christ– these desires can be displaced by turning our focus onto Jesus.
Rejoice in the Lord always. I will say it again: Rejoice! Let your gentleness be evident to all. The Lord is near. Do not be anxious about anything, but in everything, by prayer and petition, with thanksgiving, present your requests to God. And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus.
Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworthy—think about such things. Whatever you have learned or received or heard from me, or seen in me—put it into practice. And the God of peace will be with you. (Philippians 4:4-9)
Here are different ways to look at the same concept.
Since, then, you have been raised with Christ, set your hearts on things above, where Christ is seated at the right hand of God. Set your minds on things above, not on earthly things. For you died, and your life is now hidden with Christ in God. (Colossians 3:1-3)
Let us fix our eyes on Jesus, the author and perfecter of our faith, who for the joy set before him endured the cross, scorning its shame, and sat down at the right hand of the throne of God. (Hebrews 12:2)
Everyone says, "That sounds fine, but it's not that easy!" Of course it's not easy. There really is a war going on within your mind. But you can be the victor by submitting to God's thoughts about His Son. As you practice yielding to Him, the battles will become less and less intense. It takes practice –real effort and there will be many battles to face each day.
Saying to yourself "I will not think about my desires" absolutely will not achieve the wanted results. It's because that the very phrase "I will not..." becomes a law that your flesh will rebel against. You will be putting gasoline on those embers once again.
So I say, live by the Spirit, and you will not gratify the desires of the sinful nature. For the sinful nature desires what is contrary to the Spirit, and the Spirit what is contrary to the sinful nature. They are in conflict with each other, so that you do not do what you want. But if you are led by the Spirit, you are not under law. (Galatians 5:16-18)
The only path to victory is through prayer and meditation on Jesus. When you are at at rest with Him in your mind, you will also be at rest from your desires.