Our friend Isaiah says, “let us walk in the light of the Lord!” [Isaiah 2:5]
What is walking in the light? In the passage later on, verses 10-18, he mentions pride and the proud a good number of times. Before this passage he talks about the “people of Israel” [2:6] being preoccupied with the things of the world (foreign nations).
I would say that pride in the things of the world, including both our own achievements and the achievements of humankind ≠ (is not equal to) walking in the light of the Lord.
C. S. Lewis probably says something about pride being the worst of sins because it prevents you from seeking forgiveness. But I am in the middle of exams, and so…