I remember he said he had to learn how to write and perform again. But this doesn't mean he didn't know how to do it before he started with drugs. When the addiction became severe it was affecting him (remember that 106&park with 50) and after quitting drugs is not that easy.
"I had to learn to write and rap again, and I had to do it sober and 100 percent clean," Em said, explaining the more mature, focused nature of his rhymes on Recovery. "That didn't feel good at first ... I mean it in the literal sense. I actually had to learn how to say my lyrics again #8212; how to phrase them, make them flow, how to use force so they sounded like I meant them. Rapping wasn't like riding a bike. It was [as much] physical as mental. I was relearning basic motor skills. I couldn't control my hand shakes. I'd get in the [recording] booth and tried to rap, and none of it was clever, none was witty and I wasn't saying it right."
http://www.mtv.com/news/articles/164779 ... gain.jhtml