Psalm 19:8
the precepts of the Lord are right, rejoicing the heart; the commandment of the Lord is pure, enlightening the eyes
God's revelation to us - about himself, ourselves and how life works - is right and pure, unlike the ideas we invent for ourselves about how we think the world does or should work. It would seem ridiculous for me to claim to be an expert in Physics compared to Einstein for example, but we all seem to think that we're an expert in life. Maybe God, the creator of life, can give us a bit of advice, but otherwise we've pretty much got it sorted! We are self proclaimed experts on life but we are actually walking around in darkness.
proverbs 14:12 There is a way that seems right to a man, but its end is the way to death.
"only in the commandments of God that we find the difference between good and evil laid down, and that it is in vain to seek it elsewhere, since whatever men devise of themselves is mere filth and refuse, corrupting the purity of the life. He farther intimates that men, with all their acuteness, are blind, and always wander in darkness, until they turn their eyes to the light of heavenly doctrine. Whence it follows, that none are truly wise but those who take God for their conductor and guide, following the path which he points out to them, and who are diligently seeking after the peace which he offers and presents by his word." Calvin
It's God's word that opens our eyes to see things asthey really are and that news - the depths of our sin but the wonders of his grace, should cause our hearts to rejoice.