Look inside these walls and you see them having withdrawals
Of a prisoner on his way
If you could see inside Kendrick’s mind (the facades people put up to hide their true selves are often called “walls”), you would see that his mind is currently trying to escape the dangerous environment he is in. While trying to cleanse himself of those influences, they are constantly trying to get back in (hence the withdrawals).
He’s also literally trapped — inside the “walls” of the city plagued by gang violence, and he is recognizing that his actions and the actions of those around him (i.e. gangbanging and drug using) have him already cast as a prisoner on his way to a life toiling in Compton.
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