When I was happily employed as a full-time musician many years ago, I noticed the difference between those who played music as if their life depended on it and those who didn’t.
Maybe I was just lucky, but the former description fit nearly all the rock musicians I shared a stage with, from talented local bar bands in NY and LA to concert headliners such as Sly and the Family Stone and The Grateful Dead. These musicians performed and rehearsed with urgency, with something at stake. They weren’t always playing for their livelihood but they always seemed to be playing for their life.
Unfortunately I also knew a few musicians—usually in wedding or "general business" bands—who might actually nod off during a rehearsal or gig! (Just for the record, I have nothing against wedding bands, or even weddings for that matter.) I remember when a leader of a cocktail quartet complained to me about his drummer: “I wish he would just quit.” I could only respond: “I think he did a while ago.”