Illumination & further revelations always need to be compared to previous revelation.
Example: The Bereans
Now the Bereans were of more noble character than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true. (Acts 17:11)
It's noble to be open to God's truth. However, not just anything could or should pass for "revelation." If it counters what existing revelation says--and it's up to us to examine the Bible daily to see if what XYZ says is true--then we need to reject it.
Agreed! Along with the inspiration of the Holy Ghost, you can't go wrong!