The Bible book " Proverbs" is just that, a book of sayings on how to live. Chap 4v18 is simply saying that a righteous man, the longer he practices righteousness, will find his conscience gets sharper, so he knows how to act properly, like a walker whose path is illuminated.
It has nothing to do with "Bible understanding", there was not even a collected O.T when the words were written.
Jesus' parables are just that too, just illustrations.