For my unconquerable soul.
In the fell clutch of circumstance
I have not winced nor cried aloud.
Under the bludgeonings of chance
My head is bloody, but unbowed.
Beyond this place of wrath and tears
Looms but the Horror of the shade,
And yet the menace of the years
Finds and shall find me unafraid.
It matters not how strait the gate,
How charged with punishments the scroll.
I am the master of my fate:
I am the captain of my soul.
The speaker can be anyone he wants to be. The idea of the poet asserting his strength so that he is the ‘captain’ of his soul — bringing to mind the person in command of a ship — would have chimed with the Victorian English people. Note that the patriotic song  Rule Britannia  suggests that Britons saw themselves as ‘ruling the waves’. 
 
 The two last lines are  syntactic parallels . This has a powerful, emphatic, rhythmic impact. Ultimately, you are in charge of your essence. You  control your thoughts and your destiny despite seeming to be helpless.
Invictus