Paul was a first century christian. He wrote a letter to the church in Galatia, which is modern day central and southern Turkey. He wrote this in 50 AD:
This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh. 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. But if ye be led of the Spirit, ye are not under the law. Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness, idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God. But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, meekness, temperance: against such there is no law. And they that are Christ's have crucified the flesh with the affections and lusts. (Galatians 5)
Being led by the Spirit may seem like a mystery, it's mystical. But Paul demystifies it, and tells us exactly what it means. When we have received the holy Spirit, what it means to walk in the Spirit. But how can we walk in the Spirit without the Spirit? We cannot. One can hardly accomplish it with the Spirit in them, because their flesh fights against it, all their sinful flesh that they've built up fights against the new birth and new man. But unless you see the fruit of the Spirit, do not be deceived; salvation comes with the receiving of the holy Spirit: not my opinion, not my choice of how reality works, this is just how it is by God's own words, His will, His way. One can be a very nice person, one can worship God, and one can say he excretes joy and love and peace and temperance (though probably doesn't) and we can say we have no wrath or hatred or uncleanness or lasciviousness in us, and we don't emulate. Again, any honest person knows how short they fall. But we cannot be our saviours.
https://webstersdictionary1828.com/Dictionary/Emulation
https://webstersdictionary1828.com/Dictionary/lasciviousness
When we have received the holy Spirit, that is a seed planet, God likes the whole idea of seeds, which is why it's so part of our world. When the holy Spirit enters into a believer in experience, that seed planted cannot be stopped, it will crush your flesh, it will grow despite ourselves. We cannot stop it. Jesus is going to bring you into fellowship no matter how dumb we are. By my own devices I will be an evil wicked person, a faithless selfish person. People think they're good, that's why they hate God and His Christ. There was a woman, 16, she sold nudes of herself and she said, Well I'm not as bad as the people who buy my nudes! Or of course there's men who watch porn and then think prostitutes are worse than them. In other words, people stand on ant hills and then say, See I'm higher than they! Meanwhile God's goodness is higher than outerspace. And he's looking down on two specks, one of which is on top of an even smaller speck. Humans are not good, so what? humans love the tree of the knowledge of good and evil, but Jesus wants us to take from the tree of life. And life is meant to be exactly what Paul describes as walking in the Spirit, and to walk in the flesh is death, because our flesh will eventually perish in its corruption and we will be given new bodies. Your body did not come from worms and/or sea sponges having sex 600 million years ago. We have our body and will be given a new one, whether it is for good or bad.
Goodness is fundamental, everyone knows what it is, it's just a matter of whether they want it or not. And the difference between a saved believer and the non-believer is that a disciple of Jesus wants all the goodness, whereas the natural man wants some goodness, But let me have a little bit of my badness on the side. Let me have my bit of adultery, It'll all work out anyway because I'm still not that bad, I have some goodness overall and I'm above these other sinners! Ant hill mindset. That's not how salvation works. But salvation is through Christ and understanding that He alone is the payment for sin and understanding that, we ask and receive the holy Spirit. And we walk in the Spirit. We begin to understand by the Spirit truly God's will and how we should live. And just because when we receive the Spirit that doesn't mean we don't have our flesh anymore, Paul says, Your flesh will war against the new nature from God. The naturally man thinks he has a good and bad nature but he only has one nature, the only other nature comes from God and it is beyond the knowledge of good and evil, it is life, eternal. Now that when we walk in the Spirit if we make a mistake it is a mistake, we do not do evil because we think it's okay or I'm good enough. We never stop walking, never stop ascending. We can't walk in both paths willingly. We have to choose a lane, because the middle ground and lower ground are all going to hell. And those that choose life receive life. Now we make our decision, I choose God. I'm not going to hell because I'm a pervert and hateful and sexist, my flesh might be built on all those things, but I will not let the flesh win. one has to understand who he is. He is not just his body, we have consciousness which interfaces through our brain. You damage your brain then your consciousness is going to struggle to do as you would, as Paul says. And what we want to do when we are given the gift of the Spirit is to please God and follow Him.