Out of the night that covers me,
Black as the pit from pole to pole,
I thank whatever gods may be
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.
“It matters not how strait the gate” can literally be translated to: “It doesn’t matter how narrow the opening is.” 
 “The gate” is a metaphor for difficult challenges in life, or perhaps for life itself. It doesn’t matter how much pain we are going to suffer or how many injustices we are going to face: we can meet those challenges. 
 It is also a reference to  Matthew 7:14 
 For the gate is narrow and the way is hard that leads to life, and those who find it are few. 
 We need to match this reference to Henley’s reference in stanza one to ‘whatever gods may be’. This would take it out of a specific Christian context. However, though an atheist, Henley was Victorian and would be immersed in biblical references. 
 Scrolls were used by many ancient civilizations. For example, Judaism still uses scrolls in synagogue which have special sacred meaning. So scrolls suggest that our lives are underpinned by whatever god or God we believe in. 
 Most importantly, scrolls represents fate, what is ‘written’ for us specifically, whether or not in a Christian context.  What Henley then says is that, despite destiny or fate that will affect his physical life, he is still in control of his spiritual self.
Invictus