When we prepare to preach, or teach, we often come to our subject with preset ideas. We do not come tabula rasa, but with preconceived ideas. Even when we are preaching expository messages, we sometimes think we already know everything there is to know on the Bible passage. Knowing this, it is imperative to go back and "relearn" what we know; maybe there is something we missed before, or the Holy Spirit has something to show us. 

We then need to apply what we have relearned to ourselves. We need to be constantly forming and reforming our faith. "Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?--unless indeed you fail to meet the test!" (2 Corinthians 13:5 ESV)

Even if our preconceived ideas are correct, we still need to examine them, we need to examine ourselves in light of what the Holy Spirit is teaching us. And that is not a subjective experience, rather what the Spirit says never contradicts the plain teaching of Scripture. He never says anything more, anything less, or anything other than the Word of God.