Look - KimChee - you may be paid a handful of sheckles.....but you are not yet professional. You are still experiencing a conflict between "common courtesy" and "professional obligation."
I.E. - Professional - gig is at 2:30 - you are set and ready at 2:15 - first note strikes at 2:29.99
Common Courtesy - Someone's kid barfed inside your instrument - you make excuses until 2:35 or sometime there-after.