For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
James Kraft
There is also a spiritual pride that comes when we think we are living up to God's standard of righteousness instead of trusting in Jesus for our righteousness. We have no righteousness in ourselves. It is the same old humanistic idea that when we do right God owes us.
It is the same old works salvation, and that Jesus' death on the cross is not good enough. It says we can earn our salvation through good works and lose it by sin. Then our salvation depends on us instead of Jesus alone by faith. It is pride in the heart that lets us believe that we can be good enough to go to heaven without being clothed in His righteousness. We either trust in Him or ourselves. If we trust in ourselves it is the height of spiritual pride.
Tim Maas
In his excellent book Mere Christianity (which I would recommend to anyone), the English apologist C. S. Lewis included a chapter on pride, which he called "The Great Sin" -- the sin that made Satan fall from heaven (as noted in Isaiah 14:12-15), and into which he continues to try to lead people to this day. The book is accessible in full at https://archive.org/details/MereChristianityCSL/mode/2up