Complex sentence: At the time, Stern was a heavy drinker and heroin user, missing flights and messing up; in a 2009 interview, Stern said, "If Miles wants to put you in a rehab, you know you've got something wrong".
Split into simpler sentences: At the time, Stern was a heavy drinker and heroin user. In a 2009 interview, he said, "If Miles wants to put you in a rehab, you know you've got something wrong".