I have taught and written much about the battle believers have, and will always have in this life, with their flesh. Most believers are enslaved to their flesh. Why? We were made with an insatiable desire for fulfillment. At birth we inherited our Sin Nature from Adam. We were all born that way. Prior to our salvation we sought fulfillment via it. It primarily utilized our flesh for that purpose. At our salvation through the washing of regeneration, our Sin Nature was cleansed from us. We are no longer hopeless sinners because of that.
However, if believers are not discipled correctly to become Spirit-filled, they may remain Christian babies for much too long. These believers have not learned to crucify the flesh. Instead, they still seek fulfillment from via the flesh, which is sin. The first battle that all Christians are in, is the battle to become free from the flesh’s dominance in our lives. We must learn to mortify our sins as we become Spirit-filled. We will always be in this battle, but there are victories available.