the warm rush he won't let himself remember
He tries to concentrate on all this instead of remembering what Demerol’s warm rush of utter well-being felt like, remembering the comfortable sound of the clunk of his chin against his chest.
Context
The refusal shown from the inside as an act of managed attention: Gately keeps his mind on the wraith's abstractions precisely so it won't drift to the body-memory of the drug — the warm rush of utter well-being, the specific comfortable clunk of a nodding chin. Sobriety here is not the absence of wanting but the constant redirection away from a remembered pleasure the pain is actively recommending.