Proverbs 23:7 "For as he thinks in his heart, so is he."
Because this proverb is true, one of the craftiest doctrines of demons Satan twisted is "we will ALWAYS sin until we die and receive a new body. They teach that sin is in the body! But Revelation 22:11 shows we remain as we were upon death. "11 He who is unjust, let him be unjust still; he who is filthy, let him be filthy still; he who is righteous, let him be righteous still; he who is holy, let him be holy still.”
People mock something called "sinless perfection" but that can go too far into thinking he who is filthy is a Christian covered in imputed righteousness of Jesus, another doctrine of demons. That verse in the last chapter of the Bible could have shown them the last two are true Christians.
Righteousness is Sinlessness from the beginning. Then when Jesus has matured all the fruit of the Spirit in us and we never stumble, then we are Holy which is Perfect. Both are possible in our lifetime IF you abide in Jesus. 1 John 3:24 (Righteous); John 15:3-4 (Holiness)