wishing getting high were still pleasurable
All he feels is a moment of deep wrenching loss, of wishing getting high was still pleasurable for him so he could get high. This feeling comes and goes all day every day, still.
Context
The exact interior of early sobriety, and the cruelest turn of the cage: Green doesn't wish he could get high — he wishes getting high were still pleasurable so that he could. The substance has already stopped working and he mourns it anyway, all day every day, the appetite outliving the reward it was ever for. This is the disease at its purest: not desire for a pleasure but grief for a pleasure that has died and left the desire behind, still intact, still firing.