The way to find the meaning of a word within a passage is to look at the context of the passage as a whole. This stanza from “Invictus” follows a pattern.
The speaker is saying; despite all of these adversities, “I am the captain of my soul.” So, if we take out the line with “strait” in it and replace it with the options above, which ones makes the most sense as something that the narrator would have to OVERCOME?
It matters not how UPRIGHT the gate,
It matters not how CLEAN the gate,
It matters not how FORMAL the gate,
It matters not how NARROW the gate,
Which one of these is a gate which would make it more difficult for the speaker to pass through? That’s your answer.
