In self justification a person justifies himself. There are generally three means by which he does this.
In self justification you:
Abase God – Job 32:1-2. Job was righteous in his own eyes. He justified himself rather than God. See Job 34:4-12. Far be it from God that he should do wickedness; and from the Almighty, that he should commit iniquity. Now read Job 35:2. Thinkest thou this to be right, that thou saidst, My righteousness is more than God’s?
This is why Elihu spoke on God’s behalf beginning in chapter 36. This is why God proclaimed so much about himself in chapters 38-41. After Job heard all these wonderful things about God, he answered God in Job 40:3-5 and Job 42:1-6. God was exalted and Job abased himself. When Job exalted God and abased himself, God proclaimed that Job was right and accepted, Job 42:7-8.
Exalt yourself – Lk 16:15. That which is highly esteemed among men is abomination in the sight of God. You see evidence, throughout the gospels, of the Pharisees exalting themselves. This is what Job had done in Job 31. And when the Pharisees exalted themselves, they derided Jesus, God’s Son, God manifest in the flesh, Lk 16:14.
Despise others – Lk 18:9-14. The Pharisee said, “I am not as other men are… or even as this publican”. He didn’t know that publican, but he despised him, Lk 18:9. You will look down your nose at others when you justify yourself. In Lk 10:29, the lawyer justified himself and asked who is my neighbor? In self-justification, you bring God down, you elevate yourself, and you despise others.
Conclusion: understanding these truths about self-justification will help you in two regards. First, you will understand self-righteous people better when you’re dealing with them about the gospel. Second, you will understand yourself better when you are trying to justify yourself. For more information on justification see Justification, The Doctrine.