The following text is adapted from Countee Cullen's 1926 poem "Thoughts in a Zoo."

They in their cruel traps, and we in ours,
Survey each other's rage, and pass the hours
Commserating each the other's woe,
To mitigate his own pain's fiery glow.
Man could but little proffer in exchange
Save that his cages have a larger range.
That lion with his lordily, untamed heart
Has in some man his human counterpart,
Some lofty soul in dreams and visions wrapped,
But in the stifling flesh securely trapped.

Based on the text, what challenges do humans sometimes experience?