Most believers should know the most basic Christian doctrine… that Christ, in grace, fully bore the death penalty for them at the cross.

Romans 5:6-9 (KJV) ⁶  For when we were yet without strength, in due time Christ died for the ungodly. ⁷  For scarcely for a righteous man will one die: yet peradventure for a good man some would even dare to die. ⁸  But God commendeth his love toward us, in that, while we were yet sinners, Christ died for us.  ⁹  Much more then, being now justified by his blood, we shall be saved from wrath through him.

But then believers need to know the secret of the indwelling life and power of Christ as their new overcoming life. All regenerated believers Christ have been made “free from sin” (from Sin’s power) by grace (Rom.6:14,18). They need not and should not, yield to sin when temptation arises (Rom.6:12, 13). Believers have also been made “free from the law (or operating principle) of sin and death” (Rom.8:2).

Romans 6:11-13 (KJV) ¹¹  Likewise reckon (consider) ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord. ¹²  Let not sin therefore reign in your mortal body, that ye should obey it in the lusts thereof. ¹³  Neither yield ye your members as instruments of unrighteousness unto sin: but yield yourselves unto God, as those that are alive from the dead, and your members as instruments of righteousness unto God.

But no believer is free from the pull of sin in the flesh (Rom 8:3b). Paul wrote of “the law of sin which is in my members” (Rom.7:23), that is, the old sinful Adamic self-seeking nature, with its inherent tendency to do wrong. Nor is he free from the conflict with the new nature which this involves. If the Christian would be truly spiritual and deal in a scriptural way with the ‘sin that indwells him,’ he must clearly recognize its presence; he must face the fact that while, thank God that while he is no longer “in sin,” sin is still in him so long as he lives in his human “body of Sin.” (Rom 6:6).

Romans 6:6-7 (AMP) ⁶  We know that our old (unrenewed) self was nailed to the cross with Him in order that [our] body [which is the instrument] of sin might be made ineffective and inactive for evil, that we might no longer be the slaves of sin. ⁷  For when a man dies, he is freed (loosed, delivered) from [the power of] sin [among men].

But this conflict between Christ’s “spirit of life” (the life of our new nature) that is always within ‘our spirit’ and the ‘Sin-spirit’ in our flesh body should not discourage us, The conflict itself is evidence of the ever-present new nature within us; it’s one of the true signs of salvation. The added presence of the new nature that we gained the moment be first believed, along with the old Sin-nature, causes this conflict. The Bible says about these two natures: “these are contrary the one to the other” (Gal.5:17).

Galatians 5:16-17 (AMP) ¹⁶  But I say, walk and live [habitually] in the [Holy] Spirit [responsive to and controlled and guided by the Spirit]; then you will certainly not gratify the cravings and desires of the flesh (of human nature without God). ¹⁷  For the desires of the flesh are opposed to the [Holy] Spirit, and the [desires of the] Spirit are opposed to the flesh (godless human nature); for these are antagonistic to each other [continually withstanding and in conflict with each other], so that you are not free but are prevented from doing what you desire to do.

But not only is this conflict within the believer a sure sign of salvation; it also creates within us a deep and necessary sense of our inward (soul’s) imperfection and of the infinite grace of a holy God in saving us and ministering to us daily in helping and empowering us to overcome sin’s temptation. This also gives us a more understanding approach as we proclaim “the gospel of the grace of God” to those who are as lost as we once were.

Paul’s epistles show clearly that there is nothing that will so help us to overcome sin and live pleasing to God as a proper understanding and an appreciation of what He has done for us in Christ by the cross. As we become more occupied with the “things of the Spirit” we find ourselves “walking in (accord with) the Spirit,” and Galatians 5:16 says: “Walk In The Spirit, And Ye Shall Not Fulfil The Lust (Desires) Of The Flesh.”

It is so much better to have our lives transformed by being occupied by and with Christ (2Cor. 3:18); seeing our real position and blessings in the heavenlies with Him (Col.3:1-3). We need not to assume the hopeless task of trying to improve the “old nature”; always engaged in introspection; always occupied with the flesh!