Read the stanza from Invictus and choose what the theme is?

1 John 2:16 "For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world."

Genesis 3:6 "And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat."

The same three concepts presented in the first book of the bible are repeated in one of the last books. The theme of your poem is "pride of life": the stupid declaration "I am the master of my fate, I am the captain of my soul," is spoken by a human who does not even know what fate and soul are. Fate is a story telling technique, analyzed after the story has ended. Soul is a Hebrew concept, a synonym for a living breathing creature. No man yet has breathed much longer than 120 years, just as God pronounced in Genesis 6:3. The average has always been about three score and ten, just as it says in Psalm 90:10.