"I had an addiction, Dean." At the time he'd tried to brush it off as something he needed to do, to get stronger, to increase his powers so he could defeat Lilith, and at first it had been. But then it was like any other addiction and it took hold. It was all he could think about. And looking back he could see just how much of an addiction it had been. At the time he'd been in denial.
"Just like you had an addiction to alcohol." Oh yes, Sam went there. "I had Ruby and you had a bottle - same difference!"