Sin is complicated and it is messy. One of the great challenges to fighting sin is that we don't always understand sin or see how it works. While there is no magic pill that eliminates sin from our lives, I have learned a few things about how it works that might help you in our own battles with sin.
Sin has three layers, and we often fight it at the wrong level, which is part of why we find ourselves failing to see progress. The outermost layer of sin is the behavior level. It is the most noticeable and observable and therefore the level we spend most of our time in battle. The problem is that our behaviors have a deeper root, a sin beneath the sin. This deeper root is the second layer - the layer of heart idols. Jesus says that out of the heart the mouth speaks. And that good trees (heart level) bear good fruit (behavior level), while bad trees (heart level) bear bad fruit (behavior level) (Luke 6:43-45). Over and over again, the Scriptures make it clear that our behavior is a product of what is happening inside our hearts. Finally, an even deeper level exists, which is our Christ-centered identity. Ultimately, all sin flows from a loss of understanding regarding our identity.
Why behavior is not where we do battle
The reason that we do not simply fight our sin on the behavior level is because it will not ultimately solve the real problem. Its like drinking a lot of coffee to make up for the fatigue caused by a lack of sleep. Drinking coffee may fix the immediate need, but it is the lack of sleep that needs to be remedied. Our sinful behaviors are merely an expression of the deeper sin issue that exists in our heart. If we deal with the behavior, but never fix the heart issue, then our deeper sin will reappear as a new behavior or just reemerge five years down the road as the same behavior. We must deal with the deeper sin.
For example, if someone is struggling with looking at pornography, then they need to not only eliminate the behavior, but also deal with the underlying issue. Looking at pornography is at the behavior level, and is an expression of a deeper heart idol. The deeper issue might be a need for significance, which they seek in the images on a screen. The deeper heart idol might be a need for control, which they find when they look at pornography. These deeper heart idols need to be analyzed and dealt with, or the behavior will return. Whether in the same way, or a new way, the deeper sin will always express itself in sinful behavior.
Why we still fight against the behavior
Even though we need to ultimately deal with the heart issues, changing our behavior does matter. We still need to create habits and patterns in our life that help us to fight the behavior, so that we are freed up to deal with the heart. If we are constantly expressing our anger by yelling and losing control, we will have a heard time dealing with the underlying issue that drives our anger and loss of control. If we never stop looking at pornography, we will have a hard time dealing with the deeper heart idols that express themselves in those behaviors. Creating safe-guards and fences to help us eliminate behavior, gives us the space to deal with the heart. Like the fences around a yard to keep children safe inside. It isn't restrictive, it is actually freeing. If there was no fence, there would be no playing outside. When there is a fence, there is freedom to play. In the same way, we build fences to keep us safe from our sinful behaviors, so we can deal with the deeper heart idols. I wrote about this principle in a previous post, and you can read it here.
Knowing our identity is central to fighting sin
At the deepest level, our sin is the product of a loss of identity. When we fail to recognize who we are in Christ, and what our new life means, it leads to heart idols. When we forget that we have all the significance we need in Christ, we seek it in other places. When we forget that Christ is in control, and that it is far better for us when he is (Romans 8:28), we try to gain control on our own. So in the battle with sin, we need to constantly remind ourselves of our identity in Christ.
The way to fight sin is not to degrade the good things God has given us in life, which we have turned into idols, it is to elevate Jesus and remember the goodness of the Gospel. One way to do this is to make a habit of preaching the gospel to yourself, which you can read about here. Another great resource would be read Timothy Keller's book Counterfeit Gods.
Sin is manipulative and deceptive, and therefore it is very difficult to fight. When we have a better understanding of how it works in our lives, we can see progress in the battle.