The FLESH (our human sinful nature) is diabolical and always ready to separate us from the spiritual things of God. Galatians 5:17, “For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.” Every saint of God struggles between the flesh and the spirit. I have heard some preachers teach that when a person gets saved, the old nature is forever gone, and only the new nature in Christ remains. However, it cannot be denied that even with the new nature (which is Christ in us, united with our spirit), we still have the sinful FLESH to contend with. So call it what you will, every Christian still has the old sinful flesh which is contrary to the Holy Spirit in us. The old nature may be gone, but the flesh is still here!
True perfection will not come until the Rapture of the church when we rise to meet Jesus in the air. (1st Thessalonians 4:17). We will stand before the Judgment Seat of Christ to follow (2nd Corinthians 5:9-11), where our works (the good and bad done in our body) will be judged and rewards will be given (1st Corinthians 3:6-15). Tears will flow for most saints, who wasted their time here on earth (1st Corinthians 3:11-15); while a few soulwinning saints will shine as the brightness of the stars forever (Daniel 12:3). They will shine because they will be a hero to all the people whom they led to Jesus Christ back on earth.
As believers, God's Spirit lives in us and renews us every day. Walking in the Spirit is a choice. We can ignore God and make the wrong choices, indulging in sin, losing our calm and peace of soul; or we can choose to walk in the Spirit, by bringing every thought into captivity unto obedience to Christ. ...
2nd Corinthians 10:3-6, “For though we walk in the flesh, we do not war after the flesh: (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;) Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ; And having in a readiness to revenge all disobedience, when your obedience is fulfilled.”