Psalm 119:66

Teach me good judgment (discernment) and knowledge, for I have believed and trusted and relied on your commandments.  

Our salvation opened the door for us to receive the Holy Spirit as our guide and teacher.  When we combine our study of the bible with the Holy Spirit guiding us, we can attain good judgment and knowledge.  The Holy Spirit will guide us and teach us in ways we could never accomplish ourselves.  All we have to do is ask the Holy Spirit.