The 43-year-old actor checked into a rehab centre last year to tackle his addiction to prescription drugs, but Butler said he used the substances because of his heavy work load, reported Contactmusic.
"I'm no angel but there's no one in this world I think that works harder than me," he said.
Butler took up smoking again two months ago but remembers how overwhelming the smell of smoke was during his cigarette-free period.
"I really noticed the smell of people when they smoke and it especially comes from your fingers. I can shake up to 500 hands in one night and those people ... Some of them are clean, some of them are dirty," he added.