In Isaiah 6 we have Isaiah seeing the Lord "high and lifted up". Then in v5 we see Isaiah see himself in a true light because he saw God:
Then I said, "Woe is me, for I am ruined! Because I am a man of unclean lips, And I live among a people of unclean lips; For my eyes have seen the King, the LORD of hosts."
There is a false humility called "low self-esteem" which says "I am good for nothing", but the focus is still on self. Isaiah does not have this, but he has a true humility. This is proved in verse 8:
Isaiah 6:8 Then I heard the voice of the Lord, saying, "Whom shall I send, and who will go for Us?" Then I said, "Here am I. Send me!"
Isaiah did not have 'low self-esteem' but he had true humility, which thought nothing of himself and all about the Lord - this is why he was quick to jump and be the one to serve God... he thought much of God and "forgot about" himself.
CS Lewis said, "Humility is not thinking less of yourself, but thinking of yourself less."
Isaiah is a great OT example of true humility gained after seeing the Lord in a true light.