He's a recovering addict, and this movie frames many of his actions in that light. When he first gets his diagnosis, what does he do? Deny its severity, hide it from Lou, and disregards his well-being so he can play a gig.
early on, he mentions to his sponsor (i'm assuming) that Lou had him call because he had a cigarette which he considers an overreaction because of the circumstances. If Lou, who's seen him during the recovery process felt like that even one cigarette was reason for concern, it suggests to me he may perhaps be more prone to relapsing, that he's shown in the past. like some in recovery might still regularly smoke as a replacement, coping mechanism, etc. whereas some know that even the smallest thing could lead to relapse so they stay away from everything.