"Sin has no power over you because you are not under law but under grace." (Romans 6:14)
If you are struggling with sin you are either under the law or come short in your understanding of God's love for you. I still have behaviors that are not good but I don't "struggle" against them. Those actions are better defined as "lapses." A lapse is "a mistake resulting from inattention," inattention to God's love for me & inattention to my identity BECAUSE OF JESUS. Some might prefer the wording "my identity IN JESUS" but the truth is I have no identity apart from Him. My consciousness resides in this temporary tent of flesh but I am not the flesh anymore than a camper is the tent. I don't have an identity in Christ and an identity out of Christ. My sole identity is in Him thus I prefer to say my identity is "because of Him." I'm not sometimes in & sometimes out. I am never "in the flesh". There was a distinct change called rebirth, a permanent change of identity not based on my behavior but based on His love & trustworthiness.
Looking at Ephesians 6:12
The flesh is not something you are to fight. Flesh is not something to kill, crucify, or whatever. I hear "Heresy!" being yelled at me already. Ephesians 6:12 says, "Our struggle is not against flesh and blood." So if you struggle with sin or the flesh something is wrong with your way of thinking, you are not operating under an awareness of God's gracious love for you. The flesh is not something to fight but to control, train, & teach. We must allow God to renew our minds & we must grow in the knowledge of God's love and trustworthiness because our minds are the bridge between the spirit and the flesh. Walking by the Spirit means to "set your mind on the things of the spirit." Our minds can either focus on flesh or focus on spirit. Our flesh is a faulty tent that needs to be repaired and secured. Our spirit is perfect forever and in constant oneness with God.
You don't train something by fighting it. If I trained an animal by kicking, punching, & throwing it that will not produce positive results. If there is any compliance it will be out of fear of punishment. Sound familiar? That is because the majority of Christians are taught to operate out of fear of punishment. "Keep the rules or get whipped!" Struggling against the flesh merely makes it harder to focus on the spirit. If I am in a one-on-one fight I am not thinking about how nice my grandmother is. I am captured by the conflict. I cannot focus on my good spirit while attempting to fight my flesh. The flesh isn't something you fight on the playground and leave lying in the dust. The flesh is always with you. "Present your body parts as servants to righteousness which will result in the purification of those parts" (Romans 6:19). Do you want your flesh to be the abused & angry dog that bites you or do you want it to be the channel through which you love others?
"Our struggle is against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms." The spiritual forces of evil approach us only to "steal, kill, and destroy" through deception. "The thief comes only to steal and kill and destroy; I came that they may have life, and have it abundantly" (John 10:10). Think about this for a second. Mainstream Christianity teaches "death to self" as a good thing that is a daily necessity. If your self is a bad & wicked thing why would Satan want to kill it? Why wouldn't he just let you destroy yourself? You have a good self so if you are trying to "kill yourself" every day Satan doesn't need to join in. Christ gives us abundant life. Satan wants to steal that life from us. He cannot actually do it but he can however convince you to keep yourself from experiencing that life by deceiving you into thinking that you are bad, the blood of Christ had no affect on you, & that being born again does not change your identity or spirit, it only means a ticket to heaven and an obligation to obey scriptures.
James 4:7 says, "Resist the devil and he will flee from you." Resist means to actively fight against. Many people invite the devil to a fight only to get perpetually whooped. You aren't to conjure up Satan's presence for a fight. You resist Him when he comes to you otherwise you are to pay him absolutely no mind. You resist because he is the one putting pressure on you. You aren't to put pressure on him. When he flees it doesn't say pursue him.
What if you are trying to fight the wrong thing? What if you are trying to fight your flesh when you should be training it for righteous deeds? What if you are trying to fight sin after Christ has broken its power over you? What if you aren't required to look for a fight in the faults of your flesh? What if you are only to fight Satan when he comes at you? God does not fight you. He doesn't want you to "surrender" because you are forever on the same side as Him.
Looking at Romans 8:6
"The mind set on the flesh is death." This is talking about a mind "set" on the flesh, a mindset of flesh. A mind of an unsaved person or a mind that is not aware of the righteous identity given to it because of Christ. It is not speaking of a mind that occasionally turns to the flesh to allow its destructive deeds to be done. It is a mind that uses expressions like, "I need to die to self," "I must kill myself for God," "I must crucify myself daily." The mind set on the flesh identifies itself by the flesh rather than the spirit. It thinks self is a bad thing because it sees self only as flesh. It is ignorant on what rebirth means. In practicality (not in doctrine) it thinks that being "born again" equates to "being born again after I die so I can get into heaven."
"But the mind set on the spirit is life and peace." If you lack peace then you are not setting your mind on the spirit, you have not seen or are not thinking of the perfect identity Christ has shared with you. Notice it is also life, not death. It is a mind that is aware of God's resurrection power living within. Instead of wallowing in attempts to "die to self" it rejoices in the life Christ has given it, the unending relationship with God. A Christian's spirit is sinless thus if your mind is set on the spirit you will not focus on "sin," you will not be conscious of it. When a mind is set on something it excludes things which do not pertain to whatever it is set upon. If my mind is set on driving I'm not thinking about swimming. A mind set on the spirit agrees with God, it does not focus on sin nor does it charge sin to itself. It dwells on the goodness of God not the wretchedness of the flesh.
Looking at Other Scriptures
Galatians 5:24 says, "Those who belong to Christ Jesus have crucified the flesh with its passions and desires." First note it is past tense. The flesh has already been crucified. In the bible death pictures separation. The flesh and its passions & desires have been separated from who you are, they are not a part of your identity. The flesh being dead means, not that our physical bodies have passed on but that we are dead to it, it is no longer a part of who we are. Verse 25 goes on to say, "If we live in the spirit, let us also walk in the spirit." When we belong to Christ we live by the spirit. All Christians live by the spirit, that is their only source of life. Before you are saved your spirit & body are dead because of sin. When you receive salvation Christ is in you & "your body is dead because of sin, but your spirit is alive because of righteousness" (Romans 8:10). So if you are a Christian walk by the spirit, focus on spiritual things. God is spirit. You are spirit. You are one spirit with God.
Colossians 2:9-15 says, Christ removed (circumcised) the body of the flesh. When we are immersed (baptized) in Him the flesh is removed and we become one spirit with Him. It is removed in terms of identity, not in terms of locality. We still have the same physical body we did before we were saved. Our rebirth creates a new man who is separate from the other, that man is a spirit. "Our old self (spirit, identity) was crucified with Christ, because of this our body of sin has been done away with" (Romans 6:6).
"By the spirit you put to death the deeds of the flesh" (Romans 8:13). There are two parts to this. The obvious one is to control yourself with your mind to where you do not allow the flesh to produce and carry out unloving & harmful deeds (you set your mind on the spirit). The second one, which must happen first for the other one to ever sustain, is to separate in your mind the deeds of the flesh from your identity. If you identify yourself by the deeds of the flesh (what most would think of as sin, disobedience, law breaking, etc) you will not walk by the spirit. If you don't focus on the spirit you cannot stop the flesh from producing and carrying out unloving & harmful deeds. If you still identify yourself as a sinner, even a "sinner saved by grace" you are not walking by the spirit and will not be able to "put to death the deeds of the flesh." If you tie what you do to who you are, sadly you are either clueless about what it means to be born again & blind to so much of the results of the cross or you are lapsing about God's goodness towards you.
What about Paul saying "I beat my body and make it my slave" (1 Corinthians 9:27)? Paul is referring to intensity in self-control, not self-destruction, fighting, death to self. "Everyone who competes in the games exercises self-control in all things" (1 Corinthians 9:25). He uses athletic language to picture one who trains his body to do his will. This does not picture shame, guilt, condemnation, or anything like that. Self-control is the opposite of death to self because self-control sees self as good. Mainstream Christianity teaches "death to self," the bible teaches "self-control." Paul was saying that he uses his spirit (self) to control his body so that it will serve his spiritual desires. Some creatures may require being struck to control them. Striking for training is a far cry from a fight to the death. Even at that Paul isn't talking about physical striking. He wasn't sitting around punching himself in the face. He was mainly referring to the weariness of travel to spread the gospel. He used his spirit to control his body for the sake of the gospel. There is nothing in this context about resisting sin or the like.
In 1 Timothy 1:18-19, 6:12; 2 Timothy 4:7 Paul talks about "fighting the good fight." What is he talking about, resisting sin as many would have you believe? No, as always he is pointing to the living Christ not dead sin. First he says to Timothy, "Fight the good fight, keeping faith and a good conscience." Then he says, "Fight the good fight of faith." Finally in 2 Timothy Paul says of himself, "I have fought the good fight, I have finished the course, I have kept the faith." It is all about faith. To "fight the good fight" is to "continue to actively trust Jesus in your day-to-day life." It is trusting our Lord in the face of adversity & all other situations. Trusting Christ is walking by & setting your mind on the spirit. Christ is a life giving spirit. He doesn't demand our life, He gives us His life!
Instead of God wanting you to pledge to give up the flesh's bad habits He wants you to receive His goodness to displace those harmful behaviors. This is the paradigm of life. Life does not focus on faults. Life does not seek to fight for survival. Life does not seek to die. Christ's life is not fleeting. "Our lives are hidden with Christ in God. Christ is our life" (Colossians 3:3-4).