There are plenty of things I have had faith in God for that aren’t directly recorded in the Bible, which I suspect is the same for many Christians. But I have also seen firsthand where spiritual experience can go horribly off and wrong in ways that are recognizable only when they are compared against the Biblical record. When Jesus was tempted by Satan, He countered by quoting the written Word of God. In contrast to this when the Serpent lied about God’s Word to Eve in the Garden of Eden, she had nothing reliable to refer back to as a record of what God had actually said.
Obviously our Bible contains only an infinitesimal fragment of our Christian experiences with God, but what is recorded is enough to provide us with good guidance under most conditions that come up during our lifetimes. I wouldn’t trade the life of the Spirit for anything, but I also know that some soulish experiences are vivid enough and strong enough that they can be confused for the spiritual. The Bible is really beneficial for testing the spirits and for discerning the difference in these cases or anywhere else we might be in danger of deception.