was the substance the day's meaning
It occurred to me that without some one-hitters to be able to look forward to smoking alone in the tunnel I was waking up every day feeling as though there was nothing in the day to anticipate or lend anything any meaning.
Context
Addiction's own definition arrived at cold, without a program, in the appalled voice of someone realizing it in real time: not that the drug was the best part of the day, but that it had quietly become the part that made every other part mean anything, and that with it gone nothing is worth anticipating. It is exactly the recognition the Ennet House chapters build toward — the Substance as the secret meaning of the day — reaching Hal with no meeting, no sponsor, and no word for what he's found but "appalling."