Jer 17:9 The heart [is] deceitful above all [things], and desperately wicked: who can know it?
We are warned by God
Pro 28:26 He that trusteth in his own heart is a fool: but whoso walketh wisely, he shall be delivered.
Ecc 9:3 This [is] an evil among all [things] that are done under the sun, that [there is] one event unto all: yea, also the heart of the sons of men is full of evil, and madness [is] in their heart while they live, and after that [they go] to the dead.
The problem is discernment. Many cults have been started when the founder thought he was being led by the Holy Spirit .
What we do know is the word of God is written under the inspiration of the Holy Spirit. What ever leading we feel comes from the Holy Spirit must line up with the word of God
God leads us and confirms our walk with illumination ...that is why persistant study is a requirement of our walk
No Christian should ever look on illumination as automatic. God has never promised to reveal precious and profound Biblical truths to any believer who will not search the Scriptures for himself. ( John 20:31, Acts 17:11, 2 Tim 2:15, 1 Peter 2:2.)
Amen, RnMom.
God's truth and glory are available to all who seek Him with an honest heart.
"Jesus answered him, I spake openly to the world; I ever taught in the synagogue, and in the temple, whither the Jews always resort; and in secret have I said nothing." - John 18:20.
Indeed, if I were to rely on mortal man any mortal man myself included, I would be opening the door to error for all the reasons you state. But the indwelling of the Spirit is preceded by a loving surrender to Gods will; He fills the void with Himself. It is in that abiding that the Word of God comes alive. (John 15, 17) We cannot choose our own will and at the same time abide in Him. Jesus was so full surrendered to the Fathers will that He was the express image of the Fathers person (Hebrews 1:3).
The working of the Spirit is particularly magnified in the Gospel of John and is confirmed throughout the New Testament. I shall not repeat again all of the many references already quoted here, but will add this:
Truth has always been hidden in plain view.
You have truly said the problem is discernment.