It itself, life is an obstacle
the narrator notes that without the extra trials of the ghetto, life is difficult enough.
here ‘obstacle’ is a call-back/play on the last line. a ‘block’ in someone’s path is an obstacle, so the ‘blocks’ seem to represent chunks of time in the narrator’s life.
putting it all together, time itself becomes an obstacle here (the existential strain of being alive, in other words)
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